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NAME

       vi - screen-oriented (visual) display editor

SYNOPSIS

       vi [-rR][-c command][-t tagstring][-w size][file ...]

DESCRIPTION

       This  utility  shall  be provided on systems that both support the User
       Portability Utilities option and define the POSIX2_CHAR_TERM symbol. On
       other systems it is optional.

       The vi (visual) utility is a screen-oriented text editor. Only the open
       and visual modes of the editor are described  in  IEEE Std 1003.1-2001;
       see  the line editor ex for additional editing capabilities used in vi.
       The user can switch back and forth between vi and  ex  and  execute  ex
       commands from within vi.

       This  reference  page uses the term edit buffer to describe the current
       working text. No specific implementation is implied by this  term.  All
       editing  changes are performed on the edit buffer, and no changes to it
       shall affect any file until an editor command writes the file.

       When using vi, the terminal screen acts as a window  into  the  editing
       buffer.  Changes  made  to the editing buffer shall be reflected in the
       screen display; the position of the cursor on the screen shall indicate
       the position within the editing buffer.

       Certain terminals do not have all the capabilities necessary to support
       the complete vi definition. When these commands cannot be supported  on
       such  terminals, this condition shall not produce an error message such
       as "not an editor command" or report a syntax error. The implementation
       may  either  accept the commands and produce results on the screen that
       are the result of an unsuccessful attempt to meet the  requirements  of
       this  volume  of IEEE Std 1003.1-2001 or report an error describing the
       terminal-related deficiency.

OPTIONS

       The vi  utility  shall  conform  to  the  Base  Definitions  volume  of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -c  command
              See the ex command description of the -c option.

       -r     See the ex command description of the -r option.

       -R     See the ex command description of the -R option.

       -t  tagstring
              See the ex command description of the -t option.

       -w  size
              See the ex command description of the -w option.

OPERANDS

       See  the  OPERANDS  section  of the ex command for a description of the
       operands supported by the vi command.

STDIN

       If standard input is not a terminal device, the results are  undefined.
       The  standard input consists of a series of commands and input text, as
       described in the EXTENDED DESCRIPTION section.

       If a read from the standard input returns an error, or  if  the  editor
       detects  an  end-of-file condition from the standard input, it shall be
       equivalent to a SIGHUP asynchronous event.

INPUT FILES

       See the INPUT FILES section of the ex command for a description of  the
       input files supported by the vi command.

ENVIRONMENT VARIABLES

       See  the  ENVIRONMENT  VARIABLES  section  of  the  ex  command for the
       environment variables that affect the execution of the vi command.

ASYNCHRONOUS EVENTS

       See the ASYNCHRONOUS EVENTS section of  the  ex  for  the  asynchronous
       events that affect the execution of the vi command.

STDOUT

       If standard output is not a terminal device, undefined results occur.

       Standard  output  may  be  used  for  writing  prompts to the user, for
       informational messages, and for writing lines from the file.

STDERR

       If standard output is not a terminal device, undefined results occur.

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       See the OUTPUT FILES section of the ex command for a description of the
       output files supported by the vi command.

EXTENDED DESCRIPTION

       If  the terminal does not have the capabilities necessary to support an
       unspecified portion of the vi definition, implementations  shall  start
       initially in ex mode or open mode.  Otherwise, after initialization, vi
       shall be in command mode; text input mode can  be  entered  by  one  of
       several  commands  used  to  insert or change text. In text input mode,
       <ESC> can be used to return to command mode; other uses  of  <ESC>  are
       described later in this section; see Terminate Command or Input Mode .

   Initialization in ex and vi
       See  Initialization  in  ex  and  vi  for  a  description  of ex and vi
       initialization for the vi utility.

   Command Descriptions in vi
       The following symbols are used in  this  reference  page  to  represent
       arguments to commands.

       buffer See  the  description  of  buffer  in  the  EXTENDED DESCRIPTION
              section of the ex utility; see Command Descriptions in ex .

       In open and visual mode, when a command synopsis shows both  [  buffer]
       and  [  count]  preceding  the  command  name, they can be specified in
       either order.

       count  A  positive  integer  used  as  an  optional  argument  to  most
              commands,  either  to  give  a  repeat  count or as a size. This
              argument is optional and shall default  to  1  unless  otherwise
              specified.

       The  Synopsis  lines  for  the  vi  commands  <control>-G, <control>-L,
       <control>-R, <control>-], %, &, ^, D, m, M, Q, u, U, and ZZ do not have
       count  as an optional argument. Regardless, it shall not be an error to
       specify a count to these commands, and any  specified  count  shall  be
       ignored.

       motion An  optional  trailing argument used by the !, <, >, c, d, and y
              commands, which is used to indicate  the  region  of  text  that
              shall  be  affected by the command. The motion can be either one
              of the command characters repeated or one of  several  other  vi
              commands (listed in the following table). Each of the applicable
              commands specifies the region of text matched by  repeating  the
              command;  each  command  that  can  be  used as a motion command
              specifies the region of text it affects.

       Commands  that  take  motion  arguments  operate  on  either  lines  or
       characters,  depending  on  the circumstances. When operating on lines,
       all lines  that  fall  partially  or  wholly  within  the  text  region
       specified  for  the  command  shall  be  affected.  When  operating  on
       characters, only the exact characters  in  the  specified  text  region
       shall be affected. Each motion command specifies this individually.

       When  commands  that  may  be  motion  commands  are not used as motion
       commands, they shall set the current position to the current  line  and
       column as specified.

       The following commands shall be valid cursor motion commands:

              <apostrophe>       (    -    j    H
              <carriage-return>  )    $    k    L
              <comma>            [[   %    l    M
              <control>-H        ]]   _    n    N
              <control>-N        {    ;    t    T
              <control>-P        }    ?    w    W
              <grave accent>     ^    b    B
              <newline>          +    e    E
              <space>            |    f    F
              <zero>             /    h    G

       Any  count that is specified to a command that has an associated motion
       command shall be applied to the motion command. If a count  is  applied
       to both the command and its associated motion command, the effect shall
       be multiplicative.

       The following symbols are used in this section to specify locations  in
       the edit buffer:

       current character

              The character that is currently indicated by the cursor.

       end of a line

              The  point  located between the last non- <newline> (if any) and
              the terminating <newline> of a line. For  an  empty  line,  this
              location coincides with the beginning of the line.

       end of the edit buffer

              The  location  corresponding  to the end of the last line in the
              edit buffer.

       The following symbols are used  in  this  section  to  specify  command
       actions:

       bigword
              In the POSIX locale, vi shall recognize four kinds of bigwords:

               1. A maximal sequence of non- <blank>s preceded and followed by
                  <blank>s or the beginning or end  of  a  line  or  the  edit
                  buffer

               2. One or more sequential blank lines

               3. The first character in the edit buffer

               4. The last non- <newline> in the edit buffer

       word   In the POSIX locale, vi shall recognize five kinds of words:

               1. A  maximal  sequence  of  letters,  digits, and underscores,
                  delimited at both ends by:

                   * Characters other than letters, digits, or underscores

                   * The beginning or end of a line

                   * The beginning or end of the edit buffer

               2. A maximal sequence of characters other than letters, digits,
                  underscores, or <blank>s, delimited at both ends by:

                   * A letter, digit, underscore

                   * <blank>s

                   * The beginning or end of a line

                   * The beginning or end of the edit buffer

               3. One or more sequential blank lines

               4. The first character in the edit buffer

               5. The last non- <newline> in the edit buffer

       section boundary

              A section boundary is one of the following:

               1. A line whose first character is a <form-feed>

               2. A line whose first character is an open curly brace ( '{' )

               3. A  line  whose  first character is a period and whose second
                  and third characters  match  a  two-character  pair  in  the
                  sections edit option (see ed)

               4. A  line  whose  first  character  is a period and whose only
                  other character  matches  the  first  character  of  a  two-
                  character pair in the sections edit option, where the second
                  character of the two-character pair is a <space>

               5. The first line of the edit buffer

               6. The last line of the edit buffer if the  last  line  of  the
                  edit  buffer  is  empty  or  if  it  is  a  ]] or } command;
                  otherwise, the last non- <newline> of the last line  of  the
                  edit buffer

       paragraph boundary

              A paragraph boundary is one of the following:

               1. A section boundary

               2. A  line  whose  first character is a period and whose second
                  and third characters  match  a  two-character  pair  in  the
                  paragraphs edit option (see ed)

               3. A  line  whose  first  character  is a period and whose only
                  other character  matches  the  first  character  of  a  two-
                  character  pair  in  the  paragraphs  edit option, where the
                  second character of the two-character pair is a <space>

               4. One or more sequential blank lines

       remembered search direction

              See the description of remembered search direction in ed.

       sentence boundary

              A sentence boundary is one of the following:

               1. A paragraph boundary

               2. The  first  non-  <blank>  that  occurs  after  a  paragraph
                  boundary

               3. The  first  non- <blank> that occurs after a period ( '.' ),
                  exclamation mark ( '!' ), or question mark ( '?' ), followed
                  by  two <space>s or the end of a line; any number of closing
                  parenthesis ( ')' ), closing brackets ( ']' ), double  quote
                  ( ' ),' or single quote ( '" ) characters can appear between
                  the punctuation mark and the two <space>s or end-of-line

       In the remainder of the description of the vi utility, the term "buffer
       line"  refers  to a line in the edit buffer and the term "display line"
       refers to the line or lines on the display screen used to  display  one
       buffer  line.  The  term  "current  line"  refers to a specific "buffer
       line".

       If there are display lines  on  the  screen  for  which  there  are  no
       corresponding  buffer lines because they correspond to lines that would
       be after the end of the file, they shall be displayed as a single tilde
       ( '~' ) character, plus the terminating <newline>.

       The  last  line of the screen shall be used to report errors or display
       informational messages. It shall also be used to display the input  for
       "line-oriented  commands"  (  /,  ?,  :,  and  !). When a line-oriented
       command is executed, the editor shall enter text input mode on the last
       line  on  the screen, using the respective command characters as prompt
       characters. (In the case of the ! command, the associated motion  shall
       be  entered  by the user before the editor enters text input mode.) The
       line entered by the user shall be terminated by  a  <newline>,  a  non-
       <control>-V-escaped   <carriage-return>,  or  unescaped  <ESC>.  It  is
       unspecified if more characters than require a display width  minus  one
       column number of screen columns can be entered.

       If  any  command  is  executed  that overwrites a portion of the screen
       other than the last line of the screen (for example, the ex suspend  or
       !  commands),  other  than  the  ex  shell  command,  the user shall be
       prompted for a character before the screen is refreshed  and  the  edit
       session continued.

       <tab>s  shall  take  up  the number of columns on the screen set by the
       tabstop edit option (see ed), unless there are less than that number of
       columns before the display margin that will cause the displayed line to
       be folded; in this case, they shall only take up the number of  columns
       up to that boundary.

       The  cursor  shall  be  placed  on the current line and relative to the
       current column as specified by each command described in the  following
       sections.

       In  open  mode,  if  the current line is not already displayed, then it
       shall be displayed.

       In visual mode, if the current line is not displayed,  then  the  lines
       that  are displayed shall be expanded, scrolled, or redrawn to cause an
       unspecified portion of the current line to be displayed.  If the screen
       is  redrawn,  no more than the number of display lines specified by the
       value of the window edit option shall be displayed (unless the  current
       line  cannot  be  completely  displayed  in the number of display lines
       specified by the window edit option) and  the  current  line  shall  be
       positioned  as  close  to the center of the displayed lines as possible
       (within the constraints imposed by the distance of the  line  from  the
       beginning or end of the edit buffer). If the current line is before the
       first line in the display and the screen is  scrolled,  an  unspecified
       portion  of  the  current line shall be placed on the first line of the
       display. If the current line is after the last line in the display  and
       the  screen  is  scrolled,  an  unspecified portion of the current line
       shall be placed on the last line of the display.

       In visual mode, if a line from the edit buffer (other than the  current
       line) does not entirely fit into the lines at the bottom of the display
       that are available for its presentation, the editor may choose  not  to
       display  any  portion of the line. The lines of the display that do not
       contain text from the edit buffer for this reason shall each consist of
       a single '@' character.

       In  visual  mode,  the editor may choose for unspecified reasons to not
       update lines in the display to correspond to the underlying edit buffer
       text. The lines of the display that do not correctly correspond to text
       from the edit buffer for this reason shall  consist  of  a  single  '@'
       character (plus the terminating <newline>), and the <control>-R command
       shall cause the editor to update the screen to correctly represent  the
       edit buffer.

       Open  and  visual mode commands that set the current column set it to a
       column position in the display, and not a  character  position  in  the
       line.  In  this case, however, the column position in the display shall
       be calculated for an infinite width display; for  example,  the  column
       related to a character that is part of a line that has been folded onto
       additional screen lines will be offset from  the  display  line  column
       where  the  buffer  line begins, not from the beginning of a particular
       display line.

       The display cursor column in the display is based on the value  of  the
       current column, as follows, with each rule applied in turn:

        1. If the current column is after the last display line column used by
           the displayed line, the display cursor column shall be set  to  the
           last display line column occupied by the last non- <newline> in the
           current line; otherwise, the display cursor column shall be set  to
           the current column.

        2. If  the character of which some portion is displayed in the display
           line column specified by the display cursor  column  requires  more
           than a single display line column:

            a. If  in  text  input  mode,  the  display cursor column shall be
               adjusted to the first display line column in which any  portion
               of that character is displayed.

            b. Otherwise,  the  display cursor column shall be adjusted to the
               last display line column in which any portion of that character
               is displayed.

       The  current  column  shall  not be changed by these adjustments to the
       display cursor column.

       If an error occurs during the parsing or execution of a vi command:

        * The terminal shall be alerted. Execution of  the  vi  command  shall
          stop,  and  the  cursor  (for  example, the current line and column)
          shall not be further modified.

        * Unless otherwise specified by the following command sections, it  is
          unspecified whether an informational message shall be displayed.

        * Any partially entered vi command shall be discarded.

        * If the vi command resulted from a map expansion, all characters from
          that map expansion shall be discarded, except as otherwise specified
          by the map command (see ed).

        * If  the  vi  command  resulted  from  the  execution of a buffer, no
          further commands caused by the execution  of  the  buffer  shall  be
          executed.

   Page Backwards
       Synopsis:

              [count] <control>-B

       If  in  open  mode, the <control>-B command shall behave identically to
       the z command. Otherwise, if the current line is the first line of  the
       edit buffer, it shall be an error.

       If  the  window  edit option is less than 3, display a screen where the
       last line of the display shall be some portion of:

              (current first line) -1

       otherwise, display a screen where the first line of the  display  shall
       be some portion of:

              (current first line) - count x ((window edit option) -2)

       If  this  calculation  would  result in a line that is before the first
       line of the edit buffer, the first line of the  display  shall  display
       some portion of the first line of the edit buffer.

       Current  line:  If  no  lines  from  the previous display remain on the
       screen, set to the last line of the display; otherwise, set to ( line -
       the number of new lines displayed on this screen).

       Current column: Set to non- <blank>.

   Scroll Forward
       Synopsis:

              [count] <control>-D

       If the current line is the last line of the edit buffer, it shall be an
       error.

       If no count is specified, count shall default to the  count  associated
       with  the  previous <control>-D or <control>-U command. If there was no
       previous <control>-D or <control>-U command, count shall default to the
       value of the scroll edit option.

       If  in  open mode, write lines starting with the line after the current
       line, until count lines or the last line of the file have been written.

       Current line: If the current line + count is past the last line of  the
       edit buffer, set to the last line of the edit buffer; otherwise, set to
       the current line + count.

       Current column: Set to non- <blank>.

   Scroll Forward by Line
       Synopsis:

              [count] <control>-E

       Display the line count lines after the last line currently displayed.

       If the last line of the edit buffer is displayed, it shall be an error.
       If  there  is  no  line  count  lines  after  the  last  line currently
       displayed, the last line of the display shall display some  portion  of
       the last line of the edit buffer.

       Current line: Unchanged if the previous current character is displayed;
       otherwise, set to the first line displayed.

       Current column: Unchanged.

   Page Forward
       Synopsis:

              [count] <control>-F

       If in open mode, the <control>-F command shall  behave  identically  to
       the  z  command. Otherwise, if the current line is the last line of the
       edit buffer, it shall be an error.

       If the window edit option is less than 3, display a  screen  where  the
       first line of the display shall be some portion of:

              (current last line) +1

       otherwise,  display  a screen where the first line of the display shall
       be some portion of:

              (current first line) + count x ((window edit option) -2)

       If this calculation would result in a line that is after the last  line
       of  the  edit  buffer,  the last line of the display shall display some
       portion of the last line of the edit buffer.

       Current line: If no lines from  the  previous  display  remain  on  the
       screen,  set to the first line of the display; otherwise, set to ( line
       + the number of new lines displayed on this screen).

       Current column: Set to non- <blank>.

   Display Information
       Synopsis:

              <control>-G

       This command shall be equivalent to the ex file command.

   Move Cursor Backwards
       Synopsis:

              [count] <control>-H

              [count] h

              the current erase character (see stty)

       If there are no characters before the current character on the  current
       line,  it  shall  be  an  error.  If there are less than count previous
       characters on the current line, count shall be adjusted to  the  number
       of previous characters on the line.

       If used as a motion command:

        1. The  text  region  shall  be from the character before the starting
           cursor up  to  and  including  the  countth  character  before  the
           starting cursor.

        2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current  column:  Set  to  ( column - the number of columns occupied by
       count characters ending with the previous current column).

   Move Down
       Synopsis:

              [count] <newline>

              [count] <control>-J

              [count] <control>-M

              [count] <control>-N

              [count] j

              [count] <carriage-return>

              [count] +

       If there are less than count lines after the current line in  the  edit
       buffer, it shall be an error.

       If used as a motion command:

        1. The  text region shall include the starting line and the next count
           - 1 lines.

        2. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current line: Set to current line+ count.

       Current  column:  Set  to  non-  <blank>  for  the   <carriage-return>,
       <control>-M, and + commands; otherwise, unchanged.

   Clear and Redisplay
       Synopsis:

              <control>-L

       If  in  open  mode,  clear  the  screen and redisplay the current line.
       Otherwise, clear and redisplay the screen.

       Current line: Unchanged.

       Current column: Unchanged.

   Move Up
       Synopsis:

              [count] <control>-P

              [count] k

              [count] -

       If there are less than count lines before the current line in the  edit
       buffer, it shall be an error.

       If used as a motion command:

        1. The  text  region  shall include the starting line and the previous
           count lines.

        2. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current line: Set to current line - count.

       Current column: Set to non-  <blank>  for  the  -  command;  otherwise,
       unchanged.

   Redraw Screen
       Synopsis:

              <control>-R

       If  any  lines have been deleted from the display screen and flagged as
       deleted on the terminal using the @ convention (see  the  beginning  of
       the  EXTENDED  DESCRIPTION section), they shall be redisplayed to match
       the contents of the edit buffer.

       It is unspecified whether lines flagged with @ because they do not  fit
       on the terminal display shall be affected.

       Current line: Unchanged.

       Current column: Unchanged.

   Scroll Backward
       Synopsis:

              [count] <control>-U

       If  the  current line is the first line of the edit buffer, it shall be
       an error.

       If no count is specified, count shall default to the  count  associated
       with  the  previous <control>-D or <control>-U command. If there was no
       previous <control>-D or <control>-U command, count shall default to the
       value of the scroll edit option.

       Current  line:  If  count  is  greater than the current line, set to 1;
       otherwise, set to the current line - count.

       Current column: Set to non- <blank>.

   Scroll Backward by Line
       Synopsis:

              [count] <control>-Y

       Display the line count lines before the first line currently displayed.

       If the current line is the first line of the edit buffer, it  shall  be
       an error. If this calculation would result in a line that is before the
       first line of the edit buffer, the first  line  of  the  display  shall
       display some portion of the first line of the edit buffer.

       Current line: Unchanged if the previous current character is displayed;
       otherwise, set to the first line displayed.

       Current column: Unchanged.

   Edit the Alternate File
       Synopsis:

              <control>-^

       This command shall be equivalent to  the  ex  edit  command,  with  the
       alternate pathname as its argument.

   Terminate Command or Input Mode
       Synopsis:

              <ESC>

       If  a  partial  vi  command  (as  defined  by  at least one, non- count
       character)  has  been  entered,  discard  the  count  and  the  command
       character(s).

       Otherwise,  if  no  command characters have been entered, and the <ESC>
       was the result of a map expansion, the terminal shall  be  alerted  and
       the <ESC> character shall be discarded, but it shall not be an error.

       Otherwise, it shall be an error.

       Current line: Unchanged.

       Current column: Unchanged.

   Search for tagstring
       Synopsis:

              <control>-]

       If  the  current  character  is  not  a word or <blank>, it shall be an
       error.

       This command shall be equivalent  to  the  ex  tag  command,  with  the
       argument to that command defined as follows.

       If the current character is a <blank>:

        1. Skip all <blank>s after the cursor up to the end of the line.

        2. If the end of the line is reached, it shall be an error.

       Then, the argument to the ex tag command shall be the current character
       and all subsequent characters, up to the first  non-word  character  or
       the end of the line.

   Move Cursor Forward
       Synopsis:

              [count] <space>

              [count] l  (ell)

       If  there  are  less than count non- <newline>s after the cursor on the
       current line, count shall be adjusted to the number of non-  <newline>s
       after the cursor on the line.

       If used as a motion command:

        1. If  the  current  or countth character after the cursor is the last
           non- <newline> in the line, the text region shall be  comprised  of
           the  current  character up to and including the last non- <newline>
           in the line. Otherwise, the text region shall be from  the  current
           character up to, but not including, the countth character after the
           cursor.

        2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       If there are no non- <newline>s after  the  current  character  on  the
       current line, it shall be an error.

       Current line: Unchanged.

       Current column: Set to the last column that displays any portion of the
       countth character after the current character.

   Replace Text with Results from Shell Command
       Synopsis:

              [count] ! motion shell-commands <newline>

       If the motion command is the ! command repeated:

        1. If the edit buffer is empty and no count was supplied, the  command
           shall  be  the  equivalent of the ex :read ! command, with the text
           input, and no text shall be copied to any buffer.

        2. Otherwise:

            a. If there are less than count -1 lines after the current line in
               the edit buffer, it shall be an error.

            b. The  text  region  shall  be  from  the  current line up to and
               including the next count -1 lines.

       Otherwise, the text region shall be the lines in which any character of
       the text region specified by the motion command appear.

       Any text copied to a buffer shall be in line mode.

       This  command shall be equivalent to the ex ! command for the specified
       lines.

   Move Cursor to End-of-Line
       Synopsis:

              [count] $

       It shall be an error if there are less than ( count -1) lines after the
       current line in the edit buffer.

       If used as a motion command:

        1. If count is 1:

            a. It shall be an error if the line is empty.

            b. Otherwise, the text region shall consist of all characters from
               the starting cursor to the last non-  <newline>  in  the  line,
               inclusive,  and  any  text  copied  to  a  buffer  shall  be in
               character mode.

        2. Otherwise, if the starting cursor position  is  at  or  before  the
           first  non-  <blank>  in the line, the text region shall consist of
           the current and the next count -1 lines, and any text  saved  to  a
           buffer shall be in line mode.

        3. Otherwise, the text region shall consist of all characters from the
           starting cursor to the last non- <newline>  in  the  line  that  is
           count  -1  lines forward from the current line, and any text copied
           to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the current line + count-1.

       Current column: The current column is set  to  the  last  display  line
       column  of the last non- <newline> in the line, or column position 1 if
       the line is empty.

       The current column shall be adjusted to be on  the  last  display  line
       column  of  the  last  non- <newline> of the current line as subsequent
       commands change the current line, until a command changes  the  current
       column.

   Move to Matching Character
       Synopsis:

              %

       If the character at the current position is not a parenthesis, bracket,
       or curly brace, search forward in the line to the first  one  of  those
       characters. If no such character is found, it shall be an error.

       The  matching  character  shall  be  the parenthesis, bracket, or curly
       brace matching the parenthesis, bracket, or curly brace,  respectively,
       that was at the current position or that was found on the current line.

       Matching shall be determined as follows, for an open parenthesis:

        1. Set a counter to 1.

        2. Search forwards until a parenthesis is found or the end of the edit
           buffer is reached.

        3. If the end of the edit buffer is reached, it shall be an error.

        4. If an open parenthesis is found, increment the counter by 1.

        5. If a close parenthesis is found, decrement the counter by 1.

        6. If the counter is zero,  the  current  character  is  the  matching
           character.

       Matching  for  a close parenthesis shall be equivalent, except that the
       search shall be backwards, from the starting character to the beginning
       of  the  buffer,  a close parenthesis shall increment the counter by 1,
       and an open parenthesis shall decrement the counter by 1.

       Matching for brackets and curly braces shall be equivalent, except that
       searching  shall  be done for open and close brackets or open and close
       curly braces. It is implementation-defined whether other characters are
       searched for and matched as well.

       If used as a motion command:

        1. If  the  matching  cursor was after the starting cursor in the edit
           buffer, and the starting cursor position was at or before the first
           non-  <blank> non- <newline> in the starting line, and the matching
           cursor position  was  at  or  after  the  last  non-  <blank>  non-
           <newline>  in  the  matching line, the text region shall consist of
           the current line to the matching  line,  inclusive,  and  any  text
           copied to a buffer shall be in line mode.

        2. If  the  matching cursor was before the starting cursor in the edit
           buffer, and the starting cursor position was at or after  the  last
           non-  <blank> non- <newline> in the starting line, and the matching
           cursor position was at  or  before  the  first  non-  <blank>  non-
           <newline>  in  the  matching line, the text region shall consist of
           the current line to the matching  line,  inclusive,  and  any  text
           copied to a buffer shall be in line mode.

        3. Otherwise,  the text region shall consist of the starting character
           to the matching character, inclusive, and  any  text  copied  to  a
           buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line where the matching character is located.

       Current  column:  Set  to  the  last  column  where  any portion of the
       matching character is displayed.

   Repeat Substitution
       Synopsis:

              &

       Repeat  the  previous  substitution  command.  This  command  shall  be
       equivalent  to the ex & command with the current line as its addresses,
       and without options, count, or flags.

   Return to Previous Context at Beginning of Line
       Synopsis:

              ' character

       It shall be an error if there is no line in the edit buffer  marked  by
       character.

       If used as a motion command:

        1. If  the  starting  cursor  is  after  the  marked  cursor, then the
           locations of the starting cursor and the marked cursor in the  edit
           buffer shall be logically swapped.

        2. The  text  region  shall  consist  of  the  starting line up to and
           including the marked line, and any text copied to a buffer shall be
           in line mode.

       If not used as a motion command:

       Current line: Set to the line referenced by the mark.

       Current column: Set to non- <blank>.

   Return to Previous Context
       Synopsis:

              ` character

       It  shall  be  an  error  if  the  marked line is no longer in the edit
       buffer.  If the marked line no longer contains a character in the saved
       numbered  character  position, it shall be as if the marked position is
       the first non- <blank>.

       If used as a motion command:

        1. It shall be an error if  the  marked  cursor  references  the  same
           character in the edit buffer as the starting cursor.

        2. If  the  starting  cursor  is  after  the  marked  cursor, then the
           locations of the starting cursor and the marked cursor in the  edit
           buffer shall be logically swapped.

        3. If  the  starting  line  is  empty  or the starting cursor is at or
           before the first non- <blank> non- <newline> of the starting  line,
           and the marked cursor line is empty or the marked cursor references
           the first character of the marked  cursor  line,  the  text  region
           shall  consist of all lines containing characters from the starting
           cursor to the line before the marked cursor  line,  inclusive,  and
           any text copied to a buffer shall be in line mode.

        4. Otherwise,  if the marked cursor line is empty or the marked cursor
           references a character at or before the  first  non-  <blank>  non-
           <newline>  of  the  marked cursor line, the region of text shall be
           from the starting cursor to the last non-  <newline>  of  the  line
           before  the marked cursor line, inclusive, and any text copied to a
           buffer shall be in character mode.

        5. Otherwise, the region of text shall be  from  the  starting  cursor
           (inclusive),  to the marked cursor (exclusive), and any text copied
           to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line referenced by the mark.

       Current column: Set to the last column in  which  any  portion  of  the
       character referenced by the mark is displayed.

   Return to Previous Section
       Synopsis:

              [count] [[

       Move the cursor backward through the edit buffer to the first character
       of the previous section boundary, count times.

       If used as a motion command:

        1. If the starting cursor was at the first character of  the  starting
           line or the starting line was empty, and the first character of the
           boundary was the first character of the  boundary  line,  the  text
           region  shall  consist  of the current line up to and including the
           line where the countth next boundary starts, and any text copied to
           a buffer shall be in line mode.

        2. If  the  boundary  was the last line of the edit buffer or the last
           non- <newline> of the last line of the edit buffer, the text region
           shall  consist  of  the last character in the edit buffer up to and
           including the starting character, and any text saved  to  a  buffer
           shall be in character mode.

        3. Otherwise,  the text region shall consist of the starting character
           up to but not including the first character  in  the  countth  next
           boundary,  and  any  text  copied to a buffer shall be in character
           mode.

       If not used as a motion command:

       Current line: Set to the line where the countth next  boundary  in  the
       edit buffer starts.

       Current  column:  Set  to  the  last column in which any portion of the
       first character of the countth next boundary is  displayed,  or  column
       position 1 if the line is empty.

   Move to Next Section
       Synopsis:

              [count] ]]

       Move  the cursor forward through the edit buffer to the first character
       of the next section boundary, count times.

       If used as a motion command:

        1. If the starting cursor was at the first character of  the  starting
           line or the starting line was empty, and the first character of the
           boundary was the first character of the  boundary  line,  the  text
           region  shall  consist  of the current line up to and including the
           line where the countth  previous  boundary  starts,  and  any  text
           copied to a buffer shall be in line mode.

        2. If  the  boundary  was  the first line of the edit buffer, the text
           region shall consist of the first character in the edit  buffer  up
           to but not including the starting character, and any text copied to
           a buffer shall be in character mode.

        3. Otherwise, the text region shall consist of the first character  in
           the  countth  previous section boundary up to but not including the
           starting character, and any text copied to a  buffer  shall  be  in
           character mode.

       If not used as a motion command:

       Current  line:  Set  to the line where the countth previous boundary in
       the edit buffer starts.

       Current column: Set to the last column in  which  any  portion  of  the
       first  character  of  the  countth  previous  boundary is displayed, or
       column position 1 if the line is empty.

   Move to First Non-<blank> Position on Current Line
       Synopsis:

              ^

       If used as a motion command:

        1. If the line has no non- <blank> non- <newline>s, or if  the  cursor
           is  at  the first non- <blank> non- <newline> of the line, it shall
           be an error.

        2. If the cursor is before the first non- <blank>  non-  <newline>  of
           the  line,  the  text  region  shall  be  comprised  of the current
           character, up to, but not including, the first  non-  <blank>  non-
           <newline> of the line.

        3. If the cursor is after the first non- <blank> non- <newline> of the
           line, the text region  shall  be  from  the  character  before  the
           starting  cursor  up  to  and including the first non- <blank> non-
           <newline> of the line.

        4. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to non- <blank>.

   Current and Line Above
       Synopsis:

              [count] _

       If there are less than count -1 lines after the  current  line  in  the
       edit buffer, it shall be an error.

       If used as a motion command:

        1. If count is less than 2, the text region shall be the current line.

        2. Otherwise,  the text region shall include the starting line and the
           next count -1 lines.

        3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current line: Set to current line + count -1.

       Current column: Set to non- <blank>.

   Move Back to Beginning of Sentence
       Synopsis:

              [count] (

       Move backward to the beginning of a sentence.  This  command  shall  be
       equivalent  to  the  [[  command,  with  the  exception  that  sentence
       boundaries shall be used instead of section boundaries.

   Move Forward to Beginning of Sentence
       Synopsis:

              [count] )

       Move forward to the beginning of a  sentence.  This  command  shall  be
       equivalent  to  the  ]]  command,  with  the  exception  that  sentence
       boundaries shall be used instead of section boundaries.

   Move Back to Preceding Paragraph
       Synopsis:

              [count] {

       Move back to the beginning of the  preceding  paragraph.  This  command
       shall  be  equivalent  to  the  [[  command,  with  the  exception that
       paragraph boundaries shall be used instead of section boundaries.

   Move Forward to Next Paragraph
       Synopsis:

              [count] }

       Move forward to the beginning of the next paragraph. This command shall
       be  equivalent  to  the  ]]  command, with the exception that paragraph
       boundaries shall be used instead of section boundaries.

   Move to Specific Column Position
       Synopsis:

              [count] |

       For the purposes of this command, lines  that  are  too  long  for  the
       current  display and that have been folded shall be treated as having a
       single, 1-based, number of columns.

       If there are less than count  columns  in  which  characters  from  the
       current line are displayed on the screen, count shall be adjusted to be
       the last column in which any portion of the line is  displayed  on  the
       screen.

       If used as a motion command:

        1. If  the  line  is empty, or the cursor character is the same as the
           character on the countth column of the line, it shall be an error.

        2. If the cursor is before the countth column of the  line,  the  text
           region  shall  be comprised of the current character, up to but not
           including the character on the countth column of the line.

        3. If the cursor is after the countth column of  the  line,  the  text
           region shall be from the character before the starting cursor up to
           and including the character on the countth column of the line.

        4. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in  which  any  portion  of  the
       character  that  is  displayed  in  the  count  column  of  the line is
       displayed.

   Reverse Find Character
       Synopsis:

              [count] ,

       If the last F, f, T, or t command was F, f, T, or t, this command shall
       be  equivalent  to  an  f,  F,  t, or T command, respectively, with the
       specified count and the same search character.

       If there was no previous F, f, T, or t command, it shall be an error.

   Repeat
       Synopsis:

              [count] .

       Repeat the last !, <, >, A, C, D, I, J, O, P, R, S, X, Y, a, c,  d,  i,
       o,  p,  r, s, x, y, or ~ command. It shall be an error if none of these
       commands have been executed. Commands (other than commands  that  enter
       text  input  mode)  executed  as  a result of map expansions, shall not
       change the value of the last repeatable command.

       Repeated commands with associated  motion  commands  shall  repeat  the
       motion  command as well; however, any specified count shall replace the
       count(s) that were originally specified to the repeated command or  its
       associated motion command.

       If  the  motion component of the repeated command is f, F, t, or T, the
       repeated command shall not set the remembered search character for  the
       ; and , commands.

       If  the repeated command is p or P, and the buffer associated with that
       command was a numeric buffer named with  a  number  less  than  9,  the
       buffer  associated  with  the  repeated  command shall be set to be the
       buffer named by the name of the previous buffer  logically  incremented
       by 1.

       If  the  repeated  character  is  a  text input command, the input text
       associated with that command is repeated literally:

        * Input characters are neither macro or abbreviation-expanded.

        * Input characters are not interpreted in any  special  way  with  the
          exception  that <newline>, <carriage-return>, and <control>-T behave
          as described in Input Mode Commands in vi .

       Current line: Set as described for the repeated command.

       Current column: Set as described for the repeated command.

   Find Regular Expression
       Synopsis:

              /

       If the input line contains no non- <newline>s, it shall  be  equivalent
       to  a line containing only the last regular expression encountered. The
       enhanced regular expressions supported by vi are described  in  Regular
       Expressions in ex .

       Otherwise,  the  line  shall  be  interpreted  as  one  or more regular
       expressions, optionally followed  by  an  address  offset  or  a  vi  z
       command.

       If  the  regular  expression  is not the last regular expression on the
       line, or if a line offset  or  z  command  is  specified,  the  regular
       expression  shall  be  terminated  by an unescaped '/' character, which
       shall not be used as part of the regular  expression.  If  the  regular
       expression is not the first regular expression on the line, it shall be
       preceded by zero or more <blank>s, a semicolon, zero or more  <blank>s,
       and  a leading '/' character, which shall not be interpreted as part of
       the regular expression. It shall be an error  to  precede  any  regular
       expression with any characters other than these.

       Each search shall begin from the character after the first character of
       the last match (or, if it is the first search, after  the  cursor).  If
       the  wrapscan  edit  option  is  set,  the search shall continue to the
       character before the starting cursor character; otherwise, to  the  end
       of  the edit buffer. It shall be an error if any search fails to find a
       match, and an informational message to this effect shall be displayed.

       An optional address offset (see Addressing in ex  )  can  be  specified
       after the last regular expression by including a trailing '/' character
       after the regular expression and specifying the address  offset.   This
       offset  will be from the line containing the match for the last regular
       expression specified. It shall be an error if  the  line  offset  would
       indicate  a  line  address less than 1 or greater than the last line in
       the edit buffer. An address offset of zero shall be supported. It shall
       be an error to follow the address offset with any other characters than
       <blank>s.

       If not used as a motion command, an  optional  z  command  (see  Redraw
       Window  )  can  be  specified  after  the  last  regular  expression by
       including a trailing '/' character after the regular  expression,  zero
       or more <blank>s, a 'z' , zero or more <blank>s, an optional new window
       edit option value, zero or more <blank>s, and a location character. The
       effect  shall  be as if the z command was executed after the / command.
       It shall be an error to follow the z command with any other  characters
       than <blank>s.

       The remembered search direction shall be set to forward.

       If used as a motion command:

        1. It  shall  be  an  error  if  the  last  match  references the same
           character in the edit buffer as the starting cursor.

        2. If any address  offset  is  specified,  the  last  match  shall  be
           adjusted by the specified offset as described previously.

        3. If  the starting cursor is after the last match, then the locations
           of the starting cursor and the last match in the edit buffer  shall
           be logically swapped.

        4. If  any  address offset is specified, the text region shall consist
           of all lines containing characters from the starting cursor to  the
           last  match  line, inclusive, and any text copied to a buffer shall
           be in line mode.

        5. Otherwise, if the starting line is empty or the starting cursor  is
           at  or before the first non- <blank> non- <newline> of the starting
           line, and the last match line is empty or the last match starts  at
           the  first  character of the last match line, the text region shall
           consist of all lines containing characters from the starting cursor
           to  the  line  before  the last match line, inclusive, and any text
           copied to a buffer shall be in line mode.

        6. Otherwise, if the last match line is empty or the last match begins
           at  a  character at or before the first non- <blank> non- <newline>
           of the last match line, the  region  of  text  shall  be  from  the
           current  cursor  to  the last non- <newline> of the line before the
           last match line, inclusive, and any text copied to a  buffer  shall
           be in character mode.

        7. Otherwise,  the  region  of  text  shall be from the current cursor
           (inclusive), to the first character of the last match  (exclusive),
           and any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current  line:  If  a match is found, set to the last matched line plus
       the address offset, if any; otherwise, unchanged.

       Current column: Set to the last column on  which  any  portion  of  the
       first  character in the last matched string is displayed, if a match is
       found; otherwise, unchanged.

   Move to First Character in Line
       Synopsis:

              0  (zero)

       Move to the first character on the  current  line.  The  character  '0'
       shall  not be interpreted as a command if it is immediately preceded by
       a digit.

       If used as a motion command:

        1. If the cursor character is the first  character  in  the  line,  it
           shall be an error.

        2. The  text  region  shall  be  from  the character before the cursor
           character up to and including the first character in the line.

        3. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: The last column in  which  any  portion  of  the  first
       character in the line is displayed, or if the line is empty, unchanged.

   Execute an ex Command
       Synopsis:

              :

       Execute one or more ex commands.

       If any portion of the screen other than the last line of the screen was
       overwritten by any ex  command  (except  shell),  vi  shall  display  a
       message  indicating  that it is waiting for an input from the user, and
       shall then read a character. This action may also be taken  for  other,
       unspecified reasons.

       If  the  next  character entered is a ':' , another ex command shall be
       accepted and executed. Any other character shall cause the screen to be
       refreshed and vi shall return to command mode.

       Current line: As specified for the ex command.

       Current column: As specified for the ex command.

   Repeat Find
       Synopsis:

              [count] ;

       This  command  shall  be  equivalent to the last F, f, T, or t command,
       with the specified count, and with the same search character  used  for
       the  last F, f, T, or t command. If there was no previous F, f, T, or t
       command, it shall be an error.

   Shift Left
       Synopsis:

              [count] < motion

       If the motion command is the < command repeated:

        1. If there are less than count -1 lines after the current line in the
           edit buffer, it shall be an error.

        2. The text region shall be from the current line, up to and including
           the next count -1 lines.

       Shift any line in the text region specified by  the  count  and  motion
       command  one shiftwidth (see the ex shiftwidth option) toward the start
       of the line, as described by the ex  <  command.  The  unshifted  lines
       shall be copied to the unnamed buffer in line mode.

       Current line: If the motion was from the current cursor position toward
       the end of the edit buffer, unchanged. Otherwise, set to the first line
       in  the  edit  buffer  that is part of the text region specified by the
       motion command.

       Current column: Set to non- <blank>.

   Shift Right
       Synopsis:

              [count] > motion

       If the motion command is the > command repeated:

        1. If there are less than count -1 lines after the current line in the
           edit buffer, it shall be an error.

        2. The text region shall be from the current line, up to and including
           the next count -1 lines.

       Shift any line with characters in the  text  region  specified  by  the
       count  and motion command one shiftwidth (see the ex shiftwidth option)
       away from the start of the line, as described by the ex > command.  The
       unshifted lines shall be copied into the unnamed buffer in line mode.

       Current line: If the motion was from the current cursor position toward
       the end of the edit buffer, unchanged. Otherwise, set to the first line
       in  the  edit  buffer  that is part of the text region specified by the
       motion command.

       Current column: Set to non- <blank>.

   Scan Backwards for Regular Expression
       Synopsis:

              ?

       Scan backwards; the ? command shall be equivalent to the / command (see
       Find Regular Expression ) with the following exceptions:

        1. The input prompt shall be a '?' .

        2. Each  search  shall  begin  from  the  character  before  the first
           character of the last match (or, if it is  the  first  search,  the
           character before the cursor character).

        3. The  search direction shall be from the cursor toward the beginning
           of the edit buffer, and  the  wrapscan  edit  option  shall  affect
           whether  the  search  wraps  to  the  end  of  the  edit buffer and
           continues.

        4. The remembered search direction shall be set to backward.

   Execute
       Synopsis:

              @buffer

       If the buffer is specified as @, the  last  buffer  executed  shall  be
       used. If no previous buffer has been executed, it shall be an error.

       Behave  as if the contents of the named buffer were entered as standard
       input. After each line of a line-mode buffer, and all but the last line
       of  a  character  mode buffer, behave as if a <newline> were entered as
       standard input.

       If an error occurs during this  process,  an  error  message  shall  be
       written,  and  no  more characters resulting from the execution of this
       command shall be processed.

       If a count is specified, behave as if that count were entered  as  user
       input before the characters from the @ buffer were entered.

       Current line: As specified for the individual commands.

       Current column: As specified for the individual commands.

   Reverse Case
       Synopsis:

              [count] ~

       Reverse  the  case  of  the  current  character  and  the next count -1
       characters,  such  that  lowercase  characters  that   have   uppercase
       counterparts  shall  be  changed to uppercase characters, and uppercase
       characters  that  have  lowercase  counterparts  shall  be  changed  to
       lowercase  characters,  as  prescribed by the current locale.  No other
       characters shall be affected by this command.

       If there are less than count -1 characters after the cursor in the edit
       buffer,  count  shall be adjusted to the number of characters after the
       cursor in the edit buffer minus 1.

       For the purposes of this command, the next  character  after  the  last
       non-  <newline>  on  the  line  shall be the next character in the edit
       buffer.

       Current line: Set to the line  including  the  (  count-1)th  character
       after the cursor.

       Current  column:  Set  to the last column in which any portion of the (
       count-1)th character after the cursor is displayed.

   Append
       Synopsis:

              [count] a

       Enter text input mode after the current cursor position. No  characters
       already  in  the edit buffer shall be affected by this command. A count
       shall cause the input text to be appended count -1 more  times  to  the
       end of the input.

       Current  line/column:  As  specified  for  the text input commands (see
       Input Mode Commands in vi ).

   Append at End-of-Line
       Synopsis:

              [count] A

       This command shall be equivalent to the vi command:

              $ [ count ] a

       (see Append ).

   Move Backward to Preceding Word
       Synopsis:

              [count] b

       With the exception that words are used  as  the  delimiter  instead  of
       bigwords, this command shall be equivalent to the B command.

   Move Backward to Preceding Bigword
       Synopsis:

              [count] B

       If  the edit buffer is empty or the cursor is on the first character of
       the edit buffer, it shall be an error.  If  less  than  count  bigwords
       begin  between the cursor and the start of the edit buffer, count shall
       be adjusted to the number of bigword beginnings between the cursor  and
       the start of the edit buffer.

       If used as a motion command:

        1. The  text  region  shall be from the first character of the countth
           previous bigword beginning up  to  but  not  including  the  cursor
           character.

        2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line containing the current column.

       Current column: Set to the last column upon which any part of the first
       character of the countth previous bigword is displayed.

   Change
       Synopsis:

              [buffer][count] c motion

       If the motion command is the c command repeated:

        1. The buffer text shall be in line mode.

        2. If there are less than count -1 lines after the current line in the
           edit buffer, it shall be an error.

        3. The  text region shall be from the current line up to and including
           the next count -1 lines.

       Otherwise, the buffer text mode and text region shall be  as  specified
       by the motion command.

       The  replaced  text shall be copied into buffer, if specified, and into
       the unnamed buffer. If the text to be replaced contains characters from
       more  than  a  single  line,  or  the  buffer text is in line mode, the
       replaced text shall be copied into the numeric buffers as well.

       If the buffer text is in line mode:

        1. Any lines that contain characters in the region shall  be  deleted,
           and  the  editor  shall enter text input mode at the beginning of a
           new line which shall replace the first line deleted.

        2. If the autoindent edit option is set, autoindent  characters  equal
           to  the  autoindent  characters  on the first line deleted shall be
           inserted as if entered by the user.

       Otherwise, if characters from more than one line are in the  region  of
       text:

        1. The text shall be deleted.

        2. Any  text  remaining  in  the last line in the text region shall be
           appended to the first line in the region, and the last line in  the
           region shall be deleted.

        3. The editor shall enter text input mode after the last character not
           deleted from the first line in the text region, if any;  otherwise,
           on the first column of the first line in the region.

       Otherwise:

        1. If  the  glyph  for  '$' is smaller than the region, the end of the
           region shall be marked with a '$' .

        2. The editor shall enter text input mode, overwriting the  region  of
           text.

       Current  line/column:  As  specified  for  the text input commands (see
       Input Mode Commands in vi ).

   Change to End-of-Line
       Synopsis:

              [buffer][count] C

       This command shall be equivalent to the vi command:

              [buffer][count] c$

       See the c command.

   Delete
       Synopsis:

              [buffer][count] d motion

       If the motion command is the d command repeated:

        1. The buffer text shall be in line mode.

        2. If there are less than count -1 lines after the current line in the
           edit buffer, it shall be an error.

        3. The  text region shall be from the current line up to and including
           the next count -1 lines.

       Otherwise, the buffer text mode and text region shall be  as  specified
       by the motion command.

       If  in open mode, and the current line is deleted, and the line remains
       on the display, an '@' character shall be displayed as the first  glyph
       of that line.

       Delete  the  region  of  text  into  buffer, if specified, and into the
       unnamed buffer. If the text to be deleted contains characters from more
       than  a  single  line,  or the buffer text is in line mode, the deleted
       text shall be copied into the numeric buffers, as well.

       Current line: Set to the first text region line  that  appears  in  the
       edit  buffer, unless that line has been deleted, in which case it shall
       be set to the last line in the edit buffer,  or  line  1  if  the  edit
       buffer is empty.

       Current column:

        1. If the line is empty, set to column position 1.

        2. Otherwise,  if  the  buffer  text is in line mode or the motion was
           from the cursor toward the end of the edit buffer:

            a. If a character from  the  current  line  is  displayed  in  the
               current  column,  set  to  the  last  column  that displays any
               portion of that character.

            b. Otherwise, set to the last column in which any portion  of  any
               character in the line is displayed.

        3. Otherwise, if a character is displayed in the column that began the
           text region, set to the last column that displays  any  portion  of
           that character.

        4. Otherwise,  set  to  the  last  column  in which any portion of any
           character in the line is displayed.

   Delete to End-of-Line
       Synopsis:

              [buffer] D

       Delete the text from the current position to the  end  of  the  current
       line; equivalent to the vi command:

              [buffer] d$

   Move to End-of-Word
       Synopsis:

              [count] e

       With  the  exception  that  words  are  used instead of bigwords as the
       delimiter, this command shall be equivalent to the E command.

   Move to End-of-Bigword
       Synopsis:

              [count] E

       If the edit buffer is empty it shall be an error. If  less  than  count
       bigwords  end  between the cursor and the end of the edit buffer, count
       shall be adjusted to the number of bigword endings between  the  cursor
       and the end of the edit buffer.

       If used as a motion command:

        1. The  text  region  shall  be from the last character of the countth
           next bigword up to and including the cursor character.

        2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Set to the line containing the current column.

       Current column: Set to the last column upon which any part of the  last
       character of the countth next bigword is displayed.

   Find Character in Current Line (Forward)
       Synopsis:

              [count] f character

       It shall be an error if count occurrences of the character do not occur
       after the cursor in the line.

       If used as a motion command:

        1. The text range shall  be  from  the  cursor  character  up  to  and
           including  the  countth occurrence of the specified character after
           the cursor.

        2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current column: Set to the last column in  which  any  portion  of  the
       countth  occurrence of the specified character after the cursor appears
       in the line.

   Find Character in Current Line (Reverse)
       Synopsis:

              [count] F character

       It shall be an error if count occurrences of the character do not occur
       before the cursor in the line.

       If used as a motion command:

        1. The  text  region  shall  be  from  the  countth  occurrence of the
           specified character before the cursor, up to, but not including the
           cursor character.

        2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current  column:  Set  to  the  last column in which any portion of the
       countth occurrence of the specified character before the cursor appears
       in the line.

   Move to Line
       Synopsis:

              [count] G

       If  count  is  not  specified, it shall default to the last line of the
       edit buffer. If count is greater than the last line of the edit buffer,
       it shall be an error.

       If used as a motion command:

        1. The  text  region shall be from the cursor line up to and including
           the specified line.

        2. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       Current line: Set to count if count is specified; otherwise,  the  last
       line.

       Current column: Set to non- <blank>.

   Move to Top of Screen
       Synopsis:

              [count] H

       If the beginning of the line count greater than the first line of which
       any portion appears on the display does  not  exist,  it  shall  be  an
       error.

       If used as a motion command:

        1. If in open mode, the text region shall be the current line.

        2. Otherwise,  the  text  region shall be from the starting line up to
           and including (the first line of the display + count -1).

        3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       If in open mode, this command shall set  the  current  column  to  non-
       <blank> and do nothing else.

       Otherwise, it shall set the current line and current column as follows.

       Current line: Set to (the first line of the display + count -1).

       Current column: Set to non- <blank>.

   Insert Before Cursor
       Synopsis:

              [count] i

       Enter text input mode before the current cursor position. No characters
       already in the edit buffer shall be affected by this command.  A  count
       shall  cause  the  input text to be appended count -1 more times to the
       end of the input.

       Current line/column: As specified for  the  text  input  commands  (see
       Input Mode Commands in vi ).

   Insert at Beginning of Line
       Synopsis:

              [count] I

       This command shall be equivalent to the vi command ^[ count] i.

   Join
       Synopsis:

              [count] J

       If the current line is the last line in the edit buffer, it shall be an
       error.

       This command shall be  equivalent  to  the  ex  join  command  with  no
       addresses,  and  an  ex  command  count  value  of  1  if count was not
       specified or if a count of 1 was specified, and  an  ex  command  count
       value of count -1 for any other value of count, except that the current
       line and column shall be set as follows.

       Current line: Unchanged.

       Current column: The last column in which any portion of  the  character
       following  the  last character in the initial line is displayed, or the
       last non- <newline> in the line if no characters were appended.

   Move to Bottom of Screen
       Synopsis:

              [count] L

       If the beginning of the line count less than the last line of which any
       portion appears on the display does not exist, it shall be an error.

       If used as a motion command:

        1. If in open mode, the text region shall be the current line.

        2. Otherwise,  the  text  region  shall  include  all  lines  from the
           starting cursor line to (the last line  of  the  display  -(  count
           -1)).

        3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

        1. If  in open mode, this command shall set the current column to non-
           <blank> and do nothing else.

        2. Otherwise, it shall set the current  line  and  current  column  as
           follows.

       Current line: Set to (the last line of the display -( count -1)).

       Current column: Set to non- <blank>.

   Mark Position
       Synopsis:

              m letter

       This  command  shall  be  equivalent  to  the  ex mark command with the
       specified character as an argument.

   Move to Middle of Screen
       Synopsis:

              M

       The middle line of the display shall be calculated as follows:

              (the top line of the display) + (((number of lines displayed) +1) /2) -1

       If used as a motion command:

        1. If in open mode, the text region shall be the current line.

        2. Otherwise, the  text  region  shall  include  all  lines  from  the
           starting  cursor  line  up  to and including the middle line of the
           display.

        3. Any text copied to a buffer shall be in line mode.

       If not used as a motion command:

       If in open mode, this command shall set  the  current  column  to  non-
       <blank> and do nothing else.

       Otherwise, it shall set the current line and current column as follows.

       Current line: Set to the middle line of the display.

       Current column: Set to non- <blank>.

   Repeat Regular Expression Find (Forward)
       Synopsis:

              n

       If  the remembered search direction was forward, the n command shall be
       equivalent to the vi / command with no characters entered by the  user.
       Otherwise,  it  shall  be  equivalent  to  the  vi  ?  command  with no
       characters entered by the user.

       If the n command is used as a motion command for the  !   command,  the
       editor  shall not enter text input mode on the last line on the screen,
       and shall behave as if the user entered a single '!' character  as  the
       text input.

   Repeat Regular Expression Find (Reverse)
       Synopsis:

              N

       Scan for the next match of the last pattern given to / or ?, but in the
       reverse direction; this is the reverse of n.

       If the remembered search direction was forward, the N command shall  be
       equivalent  to the vi ? command with no characters entered by the user.
       Otherwise, it  shall  be  equivalent  to  the  vi  /  command  with  no
       characters  entered  by  the user. If the N command is used as a motion
       command for the ! command, the editor shall not enter text  input  mode
       on the last line on the screen, and shall behave as if the user entered
       a single ! character as the text input.

   Insert Empty Line Below
       Synopsis:

              o

       Enter text input mode in a new line appended after the current line.  A
       count  shall cause the input text to be appended count -1 more times to
       the end of the already  added  text,  each  time  starting  on  a  new,
       appended line.

       Current  line/column:  As  specified  for  the text input commands (see
       Input Mode Commands in vi ).

   Insert Empty Line Above
       Synopsis:

              O

       Enter text input mode in a new line inserted before the  current  line.
       A  count  shall cause the input text to be appended count -1 more times
       to the end of the already added text, each  time  starting  on  a  new,
       appended line.

       Current  line/column:  As  specified  for  the text input commands (see
       Input Mode Commands in vi ).

   Put from Buffer Following
       Synopsis:

              [buffer] p

       If no buffer is specified, the unnamed buffer shall be used.

       If the buffer text is in line mode, the text shall  be  appended  below
       the  current  line, and each line of the buffer shall become a new line
       in the edit buffer. A count shall cause the buffer text to be  appended
       count  -1  more  times  to the end of the already added text, each time
       starting on a new, appended line.

       If the buffer text is in character mode, the  text  shall  be  appended
       into  the  current  line  after the cursor, and each line of the buffer
       other than the first and last shall become  a  new  line  in  the  edit
       buffer.  A  count  shall  cause the buffer text to be appended count -1
       more times to the end of the already added  text,  each  time  starting
       after the last added character.

       Current  line: If the buffer text is in line mode, set the line to line
       +1; otherwise, unchanged.

       Current column: If the buffer text is in line mode:

        1. If there is a non- <blank> in the first line of the buffer, set  to
           the  last  column on which any portion of the first non- <blank> in
           the line is displayed.

        2. If there is no non- <blank> in the first line of the buffer, set to
           the  last column on which any portion of the last non- <newline> in
           the first line of the buffer is displayed.

       If the buffer text is in character mode:

        1. If the text in the buffer is from more than a single line, then set
           to the last column on which any portion of the first character from
           the buffer is displayed.

        2. Otherwise, if the buffer is the unnamed buffer,  set  to  the  last
           column  on  which any portion of the last character from the buffer
           is displayed.

        3. Otherwise, set to the first column on  which  any  portion  of  the
           first character from the buffer is displayed.

   Put from Buffer Before
       Synopsis:

              [buffer] P

       If no buffer is specified, the unnamed buffer shall be used.

       If  the  buffer  text is in line mode, the text shall be inserted above
       the current line, and each line of the buffer shall become a  new  line
       in  the edit buffer. A count shall cause the buffer text to be appended
       count -1 more times to the end of the already  added  text,  each  time
       starting on a new, appended line.

       If  the  buffer  text  is in character mode, the text shall be inserted
       into the current line before the cursor, and each line  of  the  buffer
       other  than  the  first  and  last  shall become a new line in the edit
       buffer. A count shall cause the buffer text to  be  appended  count  -1
       more  times  to  the  end of the already added text, each time starting
       after the last added character.

       Current line: Unchanged.

       Current column: If the buffer text is in line mode:

        1. If there is a non- <blank> in the first line of the buffer, set  to
           the  last  column  on  which  any  portion  of  that  character  is
           displayed.

        2. If there is no non- <blank> in the first line of the buffer, set to
           the  last column on which any portion of the last non- <newline> in
           the first line of the buffer is displayed.

       If the buffer text is in character mode:

        1. If the buffer is the unnamed buffer, set  to  the  last  column  on
           which  any  portion  of  the  last  character  from  the  buffer is
           displayed.

        2. Otherwise, set to the first column on  which  any  portion  of  the
           first character from the buffer is displayed.

   Enter ex Mode
       Synopsis:

              Q

       Leave visual or open mode and enter ex command mode.

       Current line: Unchanged.

       Current column: Unchanged.

   Replace Character
       Synopsis:

              [count] r character

       Replace the count characters at and after the cursor with the specified
       character. If there are less than count non- <newline>s  at  and  after
       the cursor on the line, it shall be an error.

       If  character  is  <control>-V,  any  next  character  other  than  the
       <newline> shall be stripped of  any  special  meaning  and  used  as  a
       literal character.

       If  character  is  <ESC>,  no replacement shall be made and the current
       line and current column shall be unchanged.

       If character is <carriage-return> or <newline>, count new  lines  shall
       be  appended to the current line. All but the last of these lines shall
       be empty. count characters at and after the cursor shall be  discarded,
       and any remaining characters after the cursor in the current line shall
       be moved to the last of the new lines. If the autoindent edit option is
       set, they shall be preceded by the same number of autoindent characters
       found on the line from which the command was executed.

       Current  line:  Unchanged  unless  the  replacement  character   is   a
       <carriage-return> or <newline>, in which case it shall be set to line +
       count.

       Current column: Set to the last column position on which a  portion  of
       the  last  replaced  character  is  displayed,  or  if  the replacement
       character caused new lines to be created, set to non- <blank>.

   Replace Characters
       Synopsis:

              R

       Enter text input mode at the current cursor position possibly replacing
       text  on  the  current  line.  A count shall cause the input text to be
       appended count -1 more times to the end of the input.

       Current line/column: As specified for  the  text  input  commands  (see
       Input Mode Commands in vi ).

   Substitute Character
       Synopsis:

              [buffer][count] s

       This command shall be equivalent to the vi command:

              [buffer][count] c<space>

   Substitute Lines
       Synopsis:

              [buffer][count] S

       This command shall be equivalent to the vi command:

              [buffer][count] c_

   Move Cursor to Before Character (Forward)
       Synopsis:

              [count] t character

       It shall be an error if count occurrences of the character do not occur
       after the cursor in the line.

       If used as a motion command:

        1. The text region shall be from the cursor up to  but  not  including
           the countth occurrence of the specified character after the cursor.

        2. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current  column:  Set  to  the  last column in which any portion of the
       character before the countth  occurrence  of  the  specified  character
       after the cursor appears in the line.

   Move Cursor to After Character (Reverse)
       Synopsis:

              [count] T character

       It shall be an error if count occurrences of the character do not occur
       before the cursor in the line.

       If used as a motion command:

        1. If the character before the cursor is the specified  character,  it
           shall be an error.

        2. The text region shall be from the character before the cursor up to
           but not including the countth occurrence of the specified character
           before the cursor.

        3. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

       Current line: Unchanged.

       Current  column:  Set  to  the  last column in which any portion of the
       character after the  countth  occurrence  of  the  specified  character
       before the cursor appears in the line.

   Undo
       Synopsis:

              u

       This command shall be equivalent to the ex undo command except that the
       current line and current column shall be set as follows:

       Current line: Set to the first line added or changed if any; otherwise,
       move  to  the line preceding any deleted text if one exists; otherwise,
       move to line 1.

       Current column: If undoing  an  ex  command,  set  to  the  first  non-
       <blank>.

       Otherwise, if undoing a text input command:

        1. If  the  command  was a C, c, O, o, R, S, or s command, the current
           column shall be set to the  value  it  held  when  the  text  input
           command was entered.

        2. Otherwise, set to the last column in which any portion of the first
           character after the deleted text  is  displayed,  or,  if  no  non-
           <newline>s  follow the text deleted from this line, set to the last
           column in which any portion of the last non- <newline> in the  line
           is displayed, or 1 if the line is empty.

       Otherwise,  if  a  single  line  was  modified  (that  is, not added or
       deleted) by the u command:

        1. If text was added or changed, set to the last column in  which  any
           portion of the first character added or changed is displayed.

        2. If text was deleted, set to the last column in which any portion of
           the first character after the deleted text is displayed, or, if  no
           non-  <newline>s follow the deleted text, set to the last column in
           which any portion of  the  last  non-  <newline>  in  the  line  is
           displayed, or 1 if the line is empty.

       Otherwise, set to non- <blank>.

   Undo Current Line
       Synopsis:

              U

       Restore  the  current  line  to  its  state immediately before the most
       recent time that it became the current line.

       Current line: Unchanged.

       Current column: Set to the first  column  in  the  line  in  which  any
       portion of the first character in the line is displayed.

   Move to Beginning of Word
       Synopsis:

              [count] w

       With  the  exception  that  words  are used as the delimiter instead of
       bigwords, this command shall be equivalent to the W command.

   Move to Beginning of Bigword
       Synopsis:

              [count] W

       If the edit buffer is empty, it shall be an error. If  there  are  less
       than  count bigwords between the cursor and the end of the edit buffer,
       count shall be adjusted to move the cursor to the last bigword  in  the
       edit buffer.

       If used as a motion command:

        1. If  the associated command is c, count is 1, and the cursor is on a
           <blank>, the region of text shall be the current character  and  no
           further action shall be taken.

        2. If  there  are  less than count bigwords between the cursor and the
           end of the edit buffer, then the command  shall  succeed,  and  the
           region of text shall include the last character of the edit buffer.

        3. If  there  are  <blank>s or an end-of-line that precede the countth
           bigword, and the associated command is c, the region of text  shall
           be  up  to  and  including  the last character before the preceding
           <blank>s or end-of-line.

        4. If there are <blank>s or an end-of-line that precede  the  bigword,
           and  the  associated command is d or y, the region of text shall be
           up to and including the  last  <blank>  before  the  start  of  the
           bigword or end-of-line.

        5. Any text copied to a buffer shall be in character mode.

       If not used as a motion command:

        1. If the cursor is on the last character of the edit buffer, it shall
           be an error.

       Current line: Set to the line containing the current column.

       Current column: Set to the last column in which any part of  the  first
       character of the countth next bigword is displayed.

   Delete Character at Cursor
       Synopsis:

              [buffer][count] x

       Delete  the  count  characters  at and after the current character into
       buffer, if specified, and into the unnamed buffer.

       If the line is empty, it shall be an error.  If  there  are  less  than
       count  non-  <newline>s  at  and  after the cursor on the current line,
       count shall be adjusted to the number of non- <newline>s at  and  after
       the cursor.

       Current line: Unchanged.

       Current  column:  If  the  line  is  empty,  set  to column position 1.
       Otherwise, if there were count or less non- <newline>s at and after the
       cursor  on  the  current line, set to the last column that displays any
       part of the last non- <newline> of the line. Otherwise, unchanged.

   Delete Character Before Cursor
       Synopsis:

              [buffer][count] X

       Delete the count characters before the current character  into  buffer,
       if specified, and into the unnamed buffer.

       If  there are no characters before the current character on the current
       line, it shall be an error. If  there  are  less  than  count  previous
       characters  on  the current line, count shall be adjusted to the number
       of previous characters on the line.

       Current line: Unchanged.

       Current column: Set to (current column  -  the  width  of  the  deleted
       characters).

   Yank
       Synopsis:

              [buffer][count] y motion

       Copy  (yank) the region of text into buffer, if specified, and into the
       unnamed buffer.

       If the motion command is the y command repeated:

        1. The buffer shall be in line mode.

        2. If there are less than count -1 lines after the current line in the
           edit buffer, it shall be an error.

        3. The  text region shall be from the current line up to and including
           the next count -1 lines.

       Otherwise, the buffer text mode and text region shall be  as  specified
       by the motion command.

       Current line: If the motion was from the current cursor position toward
       the end of the edit buffer, unchanged. Otherwise, set to the first line
       in  the  edit  buffer  that is part of the text region specified by the
       motion command.

       Current column:

        1. If the motion was from the current cursor position toward  the  end
           of the edit buffer, unchanged.

        2. Otherwise, if the current line is empty, set to column position 1.

        3. Otherwise,  set  to  the  last column that displays any part of the
           first character in the  file  that  is  part  of  the  text  region
           specified by the motion command.

   Yank Current Line
       Synopsis:

              [buffer][count] Y

       This command shall be equivalent to the vi command:

              [buffer][count] y_

   Redraw Window
       If in open mode, the z command shall have the Synopsis:

       Synopsis:

              [count] z

       If  count  is not specified, it shall default to the window edit option
       -1. The z command shall be equivalent to the ex z command, with a  type
       character  of  =  and a count of count -2, except that the current line
       and current column shall be set as follows, and the window edit  option
       shall  not be affected. If the calculation for the count argument would
       result in a negative number, the count argument to  the  ex  z  command
       shall  be  zero.  A  blank line shall be written after the last line is
       written.

       Current line: Unchanged.

       Current column: Unchanged.

       If not in open mode, the z command shall have the following Synopsis:

       Synopsis:

              [line] z [count] character

       If line is not specified, it shall default to  the  current  line.   If
       line  is specified, but is greater than the number of lines in the edit
       buffer, it shall default to the number of lines in the edit buffer.

       If count is specified, the value of the window edit option shall be set
       to  count (as described in the ex window command), and the screen shall
       be redrawn.

       line shall be placed as specified by the following characters:

       <newline>, <carriage-return>

              Place the beginning of  the  line  on  the  first  line  of  the
              display.

       .      Place  the  beginning  of the line in the center of the display.
              The middle line of the display shall be calculated as  described
              for the M command.

       -      Place an unspecified portion of the line on the last line of the
              display.

       +      If line was specified, equivalent to the <newline> case. If line
              was  not specified, display a screen where the first line of the
              display shall be (current last line) +1. If there are  no  lines
              after the last line in the display, it shall be an error.

       ^      If  line  was specified, display a screen where the last line of
              the display shall contain an unspecified portion  of  the  first
              line  of  a  display  that  had  an  unspecified  portion of the
              specified line  on  the  last  line  of  the  display.  If  this
              calculation  results  in a line before the beginning of the edit
              buffer, display the first screen of the edit buffer.

       Otherwise, display a screen where the last line of  the  display  shall
       contain  an  unspecified  portion  of (current first line -1).  If this
       calculation results in a line before the beginning of the edit  buffer,
       it shall be an error.

       Current line: If line and the '^' character were specified:

        1. If  the  first  screen  was  displayed  as  a result of the command
           attempting to display  lines  before  the  beginning  of  the  edit
           buffer:  if  the  first  screen  was  already displayed, unchanged;
           otherwise, set to (current first line -1).

        2. Otherwise, set to the last line of the display.

       If line and the '+' character were specified, set to the first line  of
       the display.

       Otherwise, if line was specified, set to line.

       Otherwise, unchanged.

       Current column: Set to non- <blank>.

   Exit
       Synopsis:

              ZZ

       This  command  shall  be  equivalent  to  the  ex  xit  command with no
       addresses, trailing !, or filename (see the ex xit command).

   Input Mode Commands in vi
       In text input mode, the current line shall consist of zero or  more  of
       the following categories, plus the terminating <newline>:

        1. Characters preceding the text input entry point

       Characters  in  this  category  shall not be modified during text input
       mode.

        2. autoindent characters

       autoindent characters shall be automatically inserted  into  each  line
       that  is  created  in text input mode, either as a result of entering a
       <newline> or <carriage-return> while in  text  input  mode,  or  as  an
       effect  of  the  command  itself;  for  example,  O  or  o  (see the ex
       autoindent command), as if entered by the user.

       It  shall  be  possible  to  erase  autoindent  characters   with   the
       <control>-D  command;  it  is unspecified whether they can be erased by
       <control>-H, <control>-U,  and  <control>-W  characters.   Erasing  any
       autoindent character turns the glyph into erase-columns and deletes the
       character from the edit buffer, but does not change its  representation
       on the screen.

        3. Text input characters

       Text  input  characters are the characters entered by the user. Erasing
       any text input character turns the glyph into erase-columns and deletes
       the   character   from  the  edit  buffer,  but  does  not  change  its
       representation on the screen.

       Each text input character entered by the user (that  does  not  have  a
       special meaning) shall be treated as follows:

               a. The  text  input  character  shall  be  appended to the last
                  character in the edit buffer  from  the  first,  second,  or
                  third categories.

               b. If  there are no erase-columns on the screen, the text input
                  command was the R  command,  and  characters  in  the  fifth
                  category  from the original line follow the cursor, the next
                  such character shall be deleted from the edit buffer. If the
                  slowopen  edit option is not set, the corresponding glyph on
                  the screen shall become erase-columns.

               c. If there are erase-columns on the screen, as many columns as
                  they  occupy,  or  as are necessary, shall be overwritten to
                  display the text input character. (If only part of a  multi-
                  column  glyph is overwritten, the remainder shall be left on
                  the screen, and continue to be treated as erase-columns;  it
                  is  unspecified  whether  the  remainder  of  the  glyph  is
                  modified in any way.)

               d. If additional display line columns are needed to display the
                  text input character:

                   1. If  the  slowopen  edit  option  is  set, the text input
                      characters shall be displayed on subsequent display line
                      columns,  overwriting  any characters displayed in those
                      columns.

                   2. Otherwise, any  characters  currently  displayed  on  or
                      after  the  column  on  the  display line where the text
                      input character is to be displayed shall be pushed ahead
                      the  number of display line columns necessary to display
                      the rest of the text input character.

        4. Erase-columns

       Erase-columns are not logically part of the edit buffer, appearing only
       on  the screen, and may be overwritten on the screen by subsequent text
       input characters. When text input mode ends, all erase-columns shall no
       longer appear on the screen.

       Erase-columns  are  initially  the  region  of  text specified by the c
       command (see Change  );  however,  erasing  autoindent  or  text  input
       characters  causes the glyphs of the erased characters to be treated as
       erase-columns.

        5. Characters following the text region for the c command, or the text
           input entry point for all other commands

       Characters  in  this  category  shall not be modified during text input
       mode, except as specified  in  category  3.b.  for  the  R  text  input
       command,  or  as <blank>s deleted when a <newline> or <carriage-return>
       is entered.

       It is unspecified whether it is an error to attempt to erase  past  the
       beginning  of  a  line  that was created by the entry of a <newline> or
       <carriage-return> during text input mode. If it is not  an  error,  the
       editor shall behave as if the erasing character was entered immediately
       after the last text input character entered on the previous  line,  and
       all  of  the  non-  <newline>s  on the current line shall be treated as
       erase-columns.

       When text input mode is entered, or after a text input  mode  character
       is  entered (except as specified for the special characters below), the
       cursor shall be positioned as follows:

        1. On the first column that displays any  part  of  the  first  erase-
           column, if one exists

        2. Otherwise, if the slowopen edit option is set, on the first display
           line column after the last character in the first, second, or third
           categories, if one exists

        3. Otherwise,  the  first  column  that displays any part of the first
           character in the fifth category, if one exists

        4. Otherwise, the display line column after the last character in  the
           first, second, or third categories, if one exists

        5. Otherwise, on column position 1

       The  characters  that  are updated on the screen during text input mode
       are unspecified, other than that the last text  input  character  shall
       always  be  updated,  and,  if the slowopen edit option is not set, the
       current cursor character shall always be updated.

       The following specifications are for command characters entered  during
       text input mode.

   NUL
       Synopsis:

              NUL

       If  the  first  character of the text input is a NUL, the most recently
       input text shall be input as if entered by  the  user,  and  then  text
       input mode shall be exited. The text shall be input literally; that is,
       characters are neither macro or  abbreviation  expanded,  nor  are  any
       characters  interpreted  in  any  special  manner.   It  is unspecified
       whether implementations shall support more than 256 bytes of remembered
       input text.

   <control>-D
       Synopsis:

              <control>-D

       The  <control>-D  character  shall have no special meaning when in text
       input mode for a line-oriented command (see Command Descriptions in  vi
       ).

       This command need not be supported on block-mode terminals.

       If the cursor does not follow an autoindent character, or an autoindent
       character and a '0' or '^' character:

        1. If the cursor is in column position 1,  the  <control>-D  character
           shall be discarded and no further action taken.

        2. Otherwise, the <control>-D character shall have no special meaning.

       If  the  last  input character was a '0' , the cursor shall be moved to
       column position 1.

       Otherwise, if the last input character was a '^' , the cursor shall  be
       moved  to  column position 1. In addition, the autoindent level for the
       next input line shall be derived from the  same  line  from  which  the
       autoindent level for the current input line was derived.

       Otherwise,  the  cursor  shall  be  moved  back to the column after the
       previous shiftwidth (see the ex shiftwidth command) boundary.

       All of the glyphs on columns between the starting cursor  position  and
       (inclusively)  the ending cursor position shall become erase-columns as
       described in Input Mode Commands in vi .

       Current line: Unchanged.

       Current column: Set to 1 if the <control>-D was preceded by  a  '^'  or
       '0' ; otherwise, set to (column -1) -((column -2) % shiftwidth).

   <control>-H
       Synopsis:

              <control>-H

       If  in  text  input  mode for a line-oriented command, and there are no
       characters to erase, text input mode shall be  terminated,  no  further
       action  shall be done for this command, and the current line and column
       shall be unchanged.

       If there are characters other than autoindent characters that have been
       input on the current line before the cursor, the cursor shall move back
       one character.

       Otherwise, if there are  autoindent  characters  on  the  current  line
       before the cursor, it is implementation-defined whether the <control>-H
       command is an  error  or  if  the  cursor  moves  back  one  autoindent
       character.

       Otherwise, if the cursor is in column position 1 and there are previous
       lines that have been input, it is  implementation-defined  whether  the
       <control>-H  command  is  an  error  or if it is equivalent to entering
       <control>-H after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All of the glyphs on columns between the starting cursor  position  and
       (inclusively)  the ending cursor position shall become erase-columns as
       described in Input Mode Commands in vi .

       The current erase character (see stty) shall cause an equivalent action
       to  the  <control>-H  command, unless the previously inserted character
       was a backslash, in which case it shall be as if  the  literal  current
       erase character had been inserted instead of the backslash.

       Current  line:  Unchanged, unless previously input lines are erased, in
       which case it shall be set to line -1.

       Current column: Set to the first column that displays  any  portion  of
       the character backed up over.

   <newline>
       Synopsis:

              <newline>

              <carriage-return>

              <control>-J

              <control>-M

       If  input was part of a line-oriented command, text input mode shall be
       terminated and the command shall  continue  execution  with  the  input
       provided.

       Otherwise, terminate the current line. If there are no characters other
       than autoindent characters on the line,  all  characters  on  the  line
       shall be discarded. Otherwise, it is unspecified whether the autoindent
       characters in the line are modified by entering these characters.

       Continue text input mode on a new line appended after the current line.
       If  the  slowopen edit option is set, the lines on the screen below the
       current line shall not be pushed down, but the first of them  shall  be
       cleared and shall appear to be overwritten. Otherwise, the lines of the
       screen below the current line shall be pushed down.

       If the  autoindent  edit  option  is  set,  an  appropriate  number  of
       autoindent  characters  shall  be  added  as  a  prefix  to the line as
       described by the ex autoindent edit option.

       All columns after the cursor that are erase-columns  (as  described  in
       Input Mode Commands in vi ) shall be discarded.

       If  the  autoindent  edit  option  is  set,  all  <blank>s  immediately
       following the cursor shall be discarded.

       All remaining characters after the cursor shall be transferred  to  the
       new line, positioned after any autoindent characters.

       Current line: Set to current line +1.

       Current  column:  Set  to the first column that displays any portion of
       the first character after the autoindent characters on the new line, if
       any,  or the first column position after the last autoindent character,
       if any, or column position 1.

   <control>-T
       Synopsis:

              <control>-T

       The <control>-T character shall have no special meaning  when  in  text
       input  mode for a line-oriented command (see Command Descriptions in vi
       ).

       This command need not be supported on block-mode terminals.

       Behave as if the user entered the minimum number of <blank>s  necessary
       to  move  the  cursor  forward  to  the  column position after the next
       shiftwidth (see the ex shiftwidth command) boundary.

       Current line: Unchanged.

       Current  column:  Set  to  column  +  shiftwidth  -  ((column   -1)   %
       shiftwidth).

   <control>-U
       Synopsis:

              <control>-U

       If there are characters other than autoindent characters that have been
       input on the current line before the cursor, the cursor shall  move  to
       the first character input after the autoindent characters.

       Otherwise,  if  there  are  autoindent  characters  on the current line
       before the cursor, it is implementation-defined whether the <control>-U
       command is an error or if the cursor moves to the first column position
       on the line.

       Otherwise, if the cursor is in column position 1 and there are previous
       lines  that  have  been input, it is implementation-defined whether the
       <control>-U command is an error or if  it  is  equivalent  to  entering
       <control>-U after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All  of  the glyphs on columns between the starting cursor position and
       (inclusively) the ending cursor position shall become erase-columns  as
       described in Input Mode Commands in vi .

       The  current kill character (see stty) shall cause an equivalent action
       to the <control>-U command, unless the  previously  inserted  character
       was  a  backslash,  in which case it shall be as if the literal current
       kill character had been inserted instead of the backslash.

       Current line: Unchanged, unless previously input lines are  erased,  in
       which case it shall be set to line -1.

       Current  column:  Set  to the first column that displays any portion of
       the last character backed up over.

   <control>-V
       Synopsis:

              <control>-V

              <control>-Q

       Allow the entry of any subsequent character, other than <control>-J  or
       the  <newline>,  as  a  literal character, removing any special meaning
       that it may have to the editor in text input mode. If a <control>-V  or
       <control>-Q   is   entered  before  a  <control>-J  or  <newline>,  the
       <control>-V or  <control>-Q  character  shall  be  discarded,  and  the
       <control>-J  or  <newline>  shall  behave as described in the <newline>
       command character during input mode.

       For purposes of the display only, the editor shall behave as if  a  '^'
       character  was  entered,  and  the  cursor  shall  be  positioned as if
       overwriting the '^' character. When a subsequent character is  entered,
       the editor shall behave as if that character was entered instead of the
       original <control>-V or <control>-Q character.

       Current line: Unchanged.

       Current column: Unchanged.

   <control>-W
       Synopsis:

              <control>-W

       If there are characters other than autoindent characters that have been
       input on the current line before the cursor, the cursor shall move back
       over the last word preceding the cursor (including any <blank>s between
       the  end of the last word and the current cursor); the cursor shall not
       move to before the first character after  the  end  of  any  autoindent
       characters.

       Otherwise,  if  there  are  autoindent  characters  on the current line
       before the cursor, it is implementation-defined whether the <control>-W
       command is an error or if the cursor moves to the first column position
       on the line.

       Otherwise, if the cursor is in column position 1 and there are previous
       lines  that  have  been input, it is implementation-defined whether the
       <control>-W command is an error or if  it  is  equivalent  to  entering
       <control>-W after the last input character on the previous input line.

       Otherwise, it shall be an error.

       All  of  the glyphs on columns between the starting cursor position and
       (inclusively) the ending cursor position shall become erase-columns  as
       described in Input Mode Commands in vi .

       Current  line:  Unchanged, unless previously input lines are erased, in
       which case it shall be set to line -1.

       Current column: Set to the first column that displays  any  portion  of
       the last character backed up over.

   <ESC>
       Synopsis:

              <ESC>

       If input was part of a line-oriented command:

        1. If  interrupt  was entered, text input mode shall be terminated and
           the editor shall return to command  mode.  The  terminal  shall  be
           alerted.

        2. If  <ESC>  was entered, text input mode shall be terminated and the
           command shall continue execution with the input provided.

       Otherwise, terminate text input mode and return to command mode.

       Any autoindent characters entered on newly created lines that  have  no
       other non- <newline>s shall be deleted.

       Any  leading  autoindent  and  <blank>s on newly created lines shall be
       rewritten to be the minimum number of <blank>s possible.

       The screen shall be redisplayed as necessary to match the  contents  of
       the edit buffer.

       Current line: Unchanged.

       Current column:

        1. If  there are text input characters on the current line, the column
           shall be set to the last column where any portion of the last  text
           input character is displayed.

        2. Otherwise,  if  a  character  is  displayed  in the current column,
           unchanged.

        3. Otherwise, set to column position 1.

EXIT STATUS

       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.

CONSEQUENCES OF ERRORS

       When any error is encountered and the standard input is not a  terminal
       device  file,  vi shall not write the file or return to command or text
       input mode, and shall terminate with a non-zero exit status.

       Otherwise, when an unrecoverable  error  is  encountered  it  shall  be
       equivalent to a SIGHUP asynchronous event.

       Otherwise,  when  an  error  is encountered, the editor shall behave as
       specified in Command Descriptions in vi .

       The following sections are informative.

APPLICATION USAGE

       None.

EXAMPLES

       None.

RATIONALE

       See the RATIONALE for ex for more information on vi. Major portions  of
       the   vi  utility  specification  point  to  ex  to  avoid  inadvertent
       divergence. While ex and vi have historically  been  implemented  as  a
       single utility, this is not required by IEEE Std 1003.1-2001.

       It  is  recognized  that  portions  of  vi  would  be difficult, if not
       impossible, to implement satisfactorily on a block-mode terminal, or  a
       terminal  without  any  form  of  cursor  addressing,  thus it is not a
       mandatory requirement that such features should work on all  terminals.
       It  is  the intention, however, that a vi implementation should provide
       the full set of capabilities on all  terminals  capable  of  supporting
       them.

       Historically,  vi  exited  immediately  if the standard input was not a
       terminal. IEEE Std 1003.1-2001 permits,  but  does  not  require,  this
       behavior.  An end-of-file condition is not equivalent to an end-of-file
       character. A common end-of-file character, <control>-D, is historically
       a vi command.

       The  text  in the STDOUT section reflects the usage of the verb display
       in this section; some implementations of  vi  use  standard  output  to
       write  to  the terminal, but IEEE Std 1003.1-2001 does not require that
       to be the case.

       Historically, implementations reverted to open mode if the terminal was
       incapable   of   supporting  full  visual  mode.   IEEE Std 1003.1-2001
       requires this behavior. Historically,  the  open  mode  of  vi  behaved
       roughly equivalently to the visual mode, with the exception that only a
       single line from the edit buffer (one "buffer line") was  kept  current
       at any time.  This line was normally displayed on the next-to-last line
       of a terminal with cursor addressing (and the last line  performed  its
       normal  visual  functions for line-oriented commands and messages).  In
       addition, some few commands behaved differently in open  mode  than  in
       visual  mode.  IEEE Std 1003.1-2001  requires conformance to historical
       practice.

       Historically, ex and vi implementations have expected text  to  proceed
       in  the  usual  European/Latin  order  of left to right, top to bottom.
       There is no requirement in IEEE Std 1003.1-2001 that this be the  case.
       The  specification  was deliberately written using words like "before",
       "after", "first", and "last" in  order  to  permit  implementations  to
       support the natural text order of the language.

       Historically,  lines  past  the end of the edit buffer were marked with
       single tilde ( '~' ) characters; that is, if the one-based display  was
       20 lines in length, and the last line of the file was on line one, then
       lines 2-20 would contain only a single '~' character.

       Historically, the vi editor attempted to display only complete lines at
       the  bottom  of  the screen (it did display partial lines at the top of
       the screen). If a line was too long to  fit  in  its  entirety  at  the
       bottom  of  the screen, the screen lines where the line would have been
       displayed  were  displayed  as  single  '@'  characters,   instead   of
       displaying  part  of  the line.  IEEE Std 1003.1-2001 permits, but does
       not require, this behavior.  Implementations are encouraged to  attempt
       always  to  display  a  complete  line at the bottom of the screen when
       doing scrolling or screen positioning by buffer lines.

       Historically, lines marked with '@' were also used to  minimize  output
       to dumb terminals over slow lines; that is, changes local to the cursor
       were updated, but changes to lines on the screen that were not close to
       the cursor were simply marked with an '@' sign instead of being updated
       to match the current text. IEEE Std 1003.1-2001 permits, but  does  not
       require  this  feature  because  it  is  used  ever  less frequently as
       terminals become smarter and connections are faster.

   Initialization in ex and vi
       Historically, vi always had a line in the edit buffer, even if the edit
       buffer was "empty". For example:

        1. The  ex  command  =  executed  from  visual mode wrote "1" when the
           buffer was empty.

        2. Writes from visual mode of an empty edit buffer wrote  files  of  a
           single  character  (a  <newline>),  while writes from ex mode of an
           empty edit buffer wrote empty files.

        3. Put and read commands into an empty edit buffer left an empty  line
           at the top of the edit buffer.

       For  consistency,  IEEE Std 1003.1-2001  does  not  permit any of these
       behaviors.

       Historically, vi did not always return the  terminal  to  its  original
       modes;  for  example,  ICRNL was modified if it was not originally set.
       IEEE Std 1003.1-2001 does not permit this behavior.

   Command Descriptions in vi
       Motion commands are  among  the  most  complicated  aspects  of  vi  to
       describe.  With some exceptions, the text region and buffer type effect
       of a motion command on a vi command are  described  on  a  case-by-case
       basis. The descriptions of text regions in IEEE Std 1003.1-2001 are not
       intended to imply direction; that is, an inclusive region from  line  n
       to  line  n+5 is identical to a region from line n+5 to line n. This is
       of more than academic interest-movements to  marks  can  be  in  either
       direction,  and,  if  the  wrapscan  option is set, so can movements to
       search points. Historically, lines are always stored  into  buffers  in
       text  order;  that  is,  from  the start of the edit buffer to the end.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

       Historically, command counts were applied to any associated motion, and
       were  multiplicative  to any supplied motion count. For example, 2cw is
       the same as c2w, and 2c3w is  the  same  as  c6w.  IEEE Std 1003.1-2001
       requires  this  behavior. Historically, vi commands that used bigwords,
       words, paragraphs, and sentences as objects  treated  groups  of  empty
       lines,  or  lines  that  contained only <blank>s, inconsistently.  Some
       commands treated them as a single entity,  while  others  treated  each
       line  separately.  For example, the w, W, and B commands treated groups
       of empty lines as individual words; that is, the command would move the
       cursor  to  each new empty line. The e and E commands treated groups of
       empty lines as a single word; that is, the first use  would  move  past
       the  group  of  lines. The b command would just beep at the user, or if
       done from the start of the line as a motion command, fail in unexpected
       ways. If the lines contained only (or ended with) <blank>s, the w and W
       commands would just beep at the user, the E and e commands would  treat
       the  group  as  a single word, and the B and b commands would treat the
       lines  as  individual  words.  For  consistency   and   simplicity   of
       specification, IEEE Std 1003.1-2001 requires that all vi commands treat
       groups of empty or blank lines as a single entity,  and  that  movement
       through lines ending with <blank>s be consistent with other movements.

       Historically,  vi  documentation  indicated  that  any number of double
       quotes were skipped after punctuation  marks  at  sentence  boundaries;
       however,     implementations     only     skipped     single    quotes.
       IEEE Std 1003.1-2001 requires both to be skipped.

       Historically, the first and last characters in  the  edit  buffer  were
       word    boundaries.   This   historical   practice   is   required   by
       IEEE Std 1003.1-2001.

       Historically, vi attempted to update the minimum number of  columns  on
       the  screen  possible, which could lead to misleading information being
       displayed. IEEE Std 1003.1-2001 makes no requirements other  than  that
       the current character being entered is displayed correctly, leaving all
       other decisions in this area up to the implementation.

       Historically, lines were arbitrarily  folded  between  columns  of  any
       characters  that required multiple column positions on the screen, with
       the exception of tabs,  which  terminated  at  the  right-hand  margin.
       IEEE Std 1003.1-2001  permits  the  former  and  requires  the  latter.
       Implementations that do not arbitrarily break lines between columns  of
       characters  that occupy multiple column positions should not permit the
       cursor to rest on a  column  that  does  not  contain  any  part  of  a
       character.

       The  historical  vi  had a problem in that all movements were by buffer
       lines, not by display or screen lines. This is often the right thing to
       do;  for example, single line movements, such as j or k, should work on
       buffer lines. Commands like dj, or j., where .  is  a  change  command,
       only  make  sense for buffer lines. It is not, however, the right thing
       to do  for  screen  motion  or  scrolling  commands  like  <control>-D,
       <control>-F,  and  H. If the window is fairly small, using buffer lines
       in these cases can result in completely random motion; for  example,  1
       <control>-D  can  result  in  a  completely changed screen, without any
       overlap. This is clearly not what the user wanted. The problem is  even
       worse  in  the  case  of  the H, L, and M commands-as they position the
       cursor at the first non- <blank> of the line, they may all refer to the
       same location in large lines, and will result in no movement at all.

       In  addition, if the line is larger than the screen, using buffer lines
       can make it impossible to display parts of the line-there are  not  any
       commands  that  do  not display the beginning of the line in historical
       vi, and if both the beginning and end of the  line  cannot  be  on  the
       screen at the same time, the user suffers.  Finally, the page and half-
       page scrolling commands historically moved to the first non- <blank> in
       the new line. If the line is approximately the same size as the screen,
       this is inadequate because the cursor before and  after  a  <control>-D
       command will refer to the same location on the screen.

       Implementations  of  ex  and  vi  exist that do not have these problems
       because the relevant commands ( <control>-B, <control>-D,  <control>-F,
       <control>-U,  <control>-Y, <control>-E, H, L, and M) operate on display
       (screen) lines, not (edit) buffer lines.

       IEEE Std 1003.1-2001 does not permit this behavior by  default  because
       the   standard  developers  believed  that  users  would  find  it  too
       confusing. However, historical practice has been relaxed. For  example,
       ex  and  vi historically attempted, albeit sometimes unsuccessfully, to
       never put part of a line on the last lines of a screen; for example, if
       a  line  would  not  fit  in  its  entirety,  no  part  of the line was
       displayed, and the screen lines corresponding  to  the  line  contained
       single  '@' characters. This behavior is permitted, but not required by
       IEEE Std 1003.1-2001, so that it is  possible  for  implementations  to
       support  long  lines  in small screens more reasonably without changing
       the commands to be oriented to the display (instead of oriented to  the
       buffer).   IEEE Std 1003.1-2001  also permits implementations to refuse
       to edit any edit buffer containing a line that  will  not  fit  on  the
       screen in its entirety.

       The display area (for example, the value of the window edit option) has
       historically been "grown", or expanded, to display new text when  local
       movements  are  done in displays where the number of lines displayed is
       less than the maximum possible.  Expansion has  historically  been  the
       first  choice,  when  the target line is less than the maximum possible
       expansion value away.  Scrolling has historically been the next choice,
       done  when  the  target  line  is  less  than  half a display away, and
       otherwise, the screen was redrawn. There were exceptions,  however,  in
       that  ex  commands  generally  always  caused the screen to be redrawn.
       IEEE Std 1003.1-2001 does not specify a standard behavior because there
       may  be  external  issues,  such  as  connection  speed,  the number of
       characters necessary to  redraw  as  opposed  to  scroll,  or  terminal
       capabilities that implementations will have to accommodate.

       The  current  line  in IEEE Std 1003.1-2001 maps one-to-one to a buffer
       line in the file. The current column does not.  There are two different
       column values that are described by IEEE Std 1003.1-2001.  The first is
       the current column value as set by many of the vi commands. This  value
       is  remembered  for the lifetime of the editor. The second column value
       is the actual position on the screen where the cursor  rests.  The  two
       are  not  always  the same. For example, when the cursor is backed by a
       multi-column character, the actual cursor position on  the  screen  has
       historically been the last column of the character in command mode, and
       the first column of the character in input mode.

       Commands that set the current line, but that do  not  set  the  current
       cursor value (for example, j and k) attempt to get as close as possible
       to the remembered column position, so that the cursor tends to restrict
       itself  to  a  vertical  column  as  the  user moves around in the edit
       buffer.  IEEE Std 1003.1-2001  requires   conformance   to   historical
       practice,  requiring  that  the  display  location of the cursor on the
       display line be adjusted from the current column value as necessary  to
       support this historical behavior.

       Historically, only a single line (and for some terminals, a single line
       minus 1 column) of characters could be entered  by  the  user  for  the
       line-oriented  commands;  that  is, :, !, /, or ?. IEEE Std 1003.1-2001
       permits, but does not require, this limitation.

       Historically, "soft" errors in vi caused the terminal  to  be  alerted,
       but no error message was displayed. As a general rule, no error message
       was displayed for errors in command execution in  vi,  when  the  error
       resulted  from  the user attempting an invalid or impossible action, or
       when a searched-for object was  not  found.  Examples  of  soft  errors
       included  h  at  the left margin, <control>-B or [[ at the beginning of
       the file, 2G at the end of the file, and so  on.  In  addition,  errors
       such as %, ]], }, ), N, n, f, F, t, and T failing to find the searched-
       for object were soft as well. Less consistently, / and ?  displayed  an
       error message if the pattern was not found, /, ?, N, and n displayed an
       error message if no previous regular expression had been specified, and
       ; did not display an error message if no previous f, F, t, or T command
       had occurred. Also, behavior in this area might reasonably be based  on
       a  runtime  evaluation  of the speed of a network connection.  Finally,
       some implementations have provided error messages for  soft  errors  in
       order  to  assist  naive  users,  based  on the value of a verbose edit
       option. IEEE Std 1003.1-2001 does not list specific errors for which an
       error  message  shall  be displayed.  Implementations should conform to
       historical practice in the absence of any strong reason to diverge.

   Page Backwards
       The <control>-B and <control>-F commands historically considered it  an
       error to attempt to page past the beginning or end of the file, whereas
       the <control>-D and <control>-U commands simply moved to the  beginning
       or end of the file.  For consistency, IEEE Std 1003.1-2001 requires the
       latter behavior for all four commands. All four commands still consider
       it  an  error  if  the  current line is at the beginning ( <control>-B,
       <control>-U)  or  end  (  <control>-F,  <control>-D)   of   the   file.
       Historically,  the  <control>-B and <control>-F commands skip two lines
       in order to include overlapping lines when a single command is entered.
       This  makes less sense in the presence of a count, as there will be, by
       definition, no  overlapping  lines.  The  actual  calculation  used  by
       historical implementations of the vi editor for <control>-B was:

              ((current first line) - count x (window edit option)) +2

       and for <control>-F was:

              ((current first line) + count x (window edit option)) -2

       This  calculation does not work well when intermixing commands with and
       without counts;  for  example,  3  <control>-F  is  not  equivalent  to
       entering  the <control>-F command three times, and is not reversible by
       entering the <control>-B command  three  times.  For  consistency  with
       other  vi  commands  that  take counts, IEEE Std 1003.1-2001 requires a
       different calculation.

   Scroll Forward
       The 4BSD and System V implementations of vi  differed  on  the  initial
       value used by the scroll command. 4BSD used:

              ((window edit option) +1) /2

       while  System  V used the value of the scroll edit option. The System V
       version is  specified  by  IEEE Std 1003.1-2001  because  the  standard
       developers believed that it was more intuitive and permitted the user a
       method of setting the scroll value initially without also  setting  the
       number of lines that are displayed.

   Scroll Forward by Line
       Historically, the <control>-E and <control>-Y commands considered it an
       error if the last and first lines, respectively, were  already  on  the
       screen.   IEEE Std 1003.1-2001   requires   conformance  to  historical
       practice. Historically, the <control>-E and <control>-Y commands had no
       effect  in open mode.  For simplicity and consistency of specification,
       IEEE Std 1003.1-2001 requires that they behave as usual, albeit with  a
       single line screen.

   Clear and Redisplay
       The  historical  <control>-L command refreshed the screen exactly as it
       was supposed to be currently displayed, replacing  any  '@'  characters
       for  lines  that  had  been  deleted but not updated on the screen with
       refreshed '@' characters.  The intent of the <control>-L command is  to
       refresh when the screen has been accidentally overwritten; for example,
       by a write command from another user, or modem noise.

   Redraw Screen
       The historical <control>-R command redisplayed only when  necessary  to
       update  lines  that  had been deleted but not updated on the screen and
       that were flagged with '@' characters. There is no requirement that the
       screen  be  in any way refreshed if no lines of this form are currently
       displayed. IEEE Std 1003.1-2001 permits implementations to extend  this
       command  to  refresh  lines  on  the screen flagged with '@' characters
       because they are too long to be displayed  in  the  current  framework;
       however, the current line and column need not be modified.

   Search for tagstring
       Historically,  the  first  non-  <blank> at or after the cursor was the
       first  character,  and  all  subsequent  characters  that   were   word
       characters, up to the end of the line, were included. For example, with
       the cursor on the leading space or on the '#'  character  in  the  text
       "#bar@"  , the tag was "#bar" . On the character 'b' it was "bar" , and
       on the 'a' it was "ar" . IEEE Std 1003.1-2001 requires this behavior.

   Replace Text with Results from Shell Command
       Historically, the <, >, and ! commands considered most  cursor  motions
       other  than  line-oriented  motions  an error; for example, the command
       >/foo<CR> succeeded, while the command >l failed, even though the  text
       region   described  by  the  two  commands  might  be  identical.   For
       consistency, all three commands only  consider  entire  lines  and  not
       partial  lines,  and  the region is defined as any line that contains a
       character that was specified by the motion.

   Move to Matching Character
       Other matching characters  have  been  left  implementation-defined  in
       order  to  allow  extensions such as matching '<' and '>' for searching
       HTML, or #ifdef, #else, and #endif for searching C source.

   Repeat Substitution
       IEEE Std 1003.1-2001 requires that any c and g flags specified  to  the
       previous  substitute  command be ignored; however, the r flag may still
       apply, if supported by the implementation.

   Return to Previous (Context or Section)
       The [[, ]], (, ), {, and  }  commands  are  all  affected  by  "section
       boundaries",  but  in  some  historical  implementations not all of the
       commands recognize the same section boundaries. This is a  bug,  not  a
       feature,  and a unique section-boundary algorithm was not described for
       each command.  One special case that is preserved is that the  sentence
       command  moves to the end of the last line of the edit buffer while the
       other  commands  go  to  the  beginning,  in  order  to  preserve   the
       traditional   character   cut   semantics   of  the  sentence  command.
       Historically, vi section boundaries at the beginning  and  end  of  the
       edit  buffer were the first non- <blank> on the first and last lines of
       the edit buffer if one exists; otherwise, the  last  character  of  the
       first  and  last  lines  of the edit buffer if one exists.  To increase
       consistency with other section locations, this has been  simplified  by
       IEEE Std 1003.1-2001 to the first character of the first and last lines
       of the edit buffer, or the first and the last lines of the edit  buffer
       if they are empty.

       Sentence  boundaries  were  problematic in the historical vi. They were
       not only the boundaries  as  defined  for  the  section  and  paragraph
       commands,  but  they  were  the  first non- <blank> that occurred after
       those boundaries, as well. Historically, the vi section  commands  were
       documented  as  taking an optional window size as a count preceding the
       command.  This  was  not  implemented  in   historical   versions,   so
       IEEE Std 1003.1-2001  requires  that  the count repeat the command, for
       consistency with other vi commands.

   Repeat
       Historically, mapped commands other than text input commands could  not
       be  repeated  using  the period command.  IEEE Std 1003.1-2001 requires
       conformance to historical practice.

       The restrictions on  the  interpretation  of  special  characters  (for
       example,  <control>-H) in the repetition of text input mode commands is
       intended to match historical practice. For  example,  given  the  input
       sequence:

              iab<control>-H<control>-H<control>-Hdef<escape>

       the  user  should  be  informed  of an error when the sequence is first
       entered, but not during a command repetition. The character <control>-T
       is    specifically   exempted   from   this   restriction.   Historical
       implementations of vi ignored <control>-T characters that were input in
       the  original  command  during command repetition. IEEE Std 1003.1-2001
       prohibits this behavior.

   Find Regular Expression
       Historically, commands did not affect the line searched to or  from  if
       the  motion  command  was a search ( /, ?, N, n) and the final position
       was the start/end of the line. There were some special cases and vi was
       not consistent. IEEE Std 1003.1-2001 does not permit this behavior, for
       consistency. Historical implementations permitted but  were  unable  to
       handle  searches  as  motion commands that wrapped (that is, due to the
       edit option wrapscan) to the  original  location.  IEEE Std 1003.1-2001
       requires that this behavior be treated as an error.

       Historically,  the  syntax "/RE/0" was used to force the command to cut
       text  in  line  mode.  IEEE Std 1003.1-2001  requires  conformance   to
       historical practice.

       Historically,  in  open  mode,  a  z  specified  to  a  search  command
       redisplayed the current line instead of displaying the  current  screen
       with  the  current  line highlighted. For consistency and simplicity of
       specification, IEEE Std 1003.1-2001 does not permit this behavior.

       Historically, trailing z commands were permitted and ignored if entered
       as  part  of  a  search  used  as a motion command. For consistency and
       simplicity of specification, IEEE Std 1003.1-2001 does not permit  this
       behavior.

   Execute an ex Command
       Historically,  vi implementations restricted the commands that could be
       entered on the colon command line (for example, append and change), and
       some  other commands were known to cause them to fail catastrophically.
       For   consistency,   IEEE Std 1003.1-2001   does   not   permit   these
       restrictions.  When  executing  an  ex command by entering :, it is not
       possible to enter a <newline> as part of  the  command  because  it  is
       considered  the end of the command. A different approach is to enter ex
       command mode by using the vi Q command (and later resuming visual  mode
       with the ex vi command). In ex command mode, the single-line limitation
       does not exist. So, for example, the following is valid:

              Q
              s/break here/break\
              here/
              vi

       IEEE Std 1003.1-2001 requires that, if the ex  command  overwrites  any
       part  of  the screen that would be erased by a refresh, vi pauses for a
       character from the user. Historically,  this  character  could  be  any
       character;  for  example,  a  character  input  by  the user before the
       message appeared, or even a mapped character. This is probably  a  bug,
       but  implementations  that  have tried to be more rigorous by requiring
       that the user enter a specific character, or  that  the  user  enter  a
       character  after  the  message  was displayed, have been forced by user
       indignation  back  into  historical   behavior.    IEEE Std 1003.1-2001
       requires conformance to historical practice.

   Shift Left (Right)
       Refer  to  the  Rationale for the ! and / commands. Historically, the <
       and > commands sometimes moved the cursor to  the  first  non-  <blank>
       (for  example  if  the  command  was  repeated  or with _ as the motion
       command), and sometimes left it  unchanged.  IEEE Std 1003.1-2001  does
       not permit this inconsistency, requiring instead that the cursor always
       move to the first non- <blank>. Historically, the < and > commands  did
       not  support  buffer arguments, although some implementations allow the
       specification of an optional buffer. This behavior is neither  required
       nor disallowed by IEEE Std 1003.1-2001.

   Execute
       Historically,  buffers could execute other buffers, and loops, infinite
       and   otherwise,   were   possible.    IEEE Std 1003.1-2001    requires
       conformance  to  historical practice.  The * buffer syntax of ex is not
       required in vi, because it is not historical practice and has been used
       in some vi implementations to support additional scripting languages.

   Reverse Case
       Historically,  the  ~  command  ignored any associated count, and acted
       only on the characters in the current line. For consistency with  other
       vi commands, IEEE Std 1003.1-2001 requires that an associated count act
       on the next count characters, and that the command move  to  subsequent
       lines if warranted by count, to make it possible to modify large pieces
       of  text  in  a   reasonably   efficient   manner.   There   exist   vi
       implementations  that  optionally  require an associated motion command
       for the ~ command. Implementations supporting  this  functionality  are
       encouraged  to  base it on the tildedop edit option and handle the text
       regions and cursor positioning identically to the yank command.

   Append
       Historically, counts specified to the A, a, I, and i commands  repeated
       the  input  of  the  first  line  count  times,  and did not repeat the
       subsequent lines of the input text. IEEE Std 1003.1-2001 requires  that
       the entire text input be repeated count times.

   Move Backward to Preceding Word
       Historically,  vi  became confused if word commands were used as motion
       commands in empty files.  IEEE Std 1003.1-2001 requires that this be an
       error.  Historical  implementations of vi had a large number of bugs in
       the word movement commands, and they varied greatly in behavior in  the
       presence  of  empty  lines,  "words" made up of a single character, and
       lines containing only  <blank>s.  For  consistency  and  simplicity  of
       specification, IEEE Std 1003.1-2001 does not permit this behavior.

   Change to End-of-Line
       Some  historical  implementations  of  the  C command did not behave as
       described by IEEE Std 1003.1-2001 when the $ key was  remapped  because
       they  were  implemented  by  pushing the $ key onto the input queue and
       reprocessing it.  IEEE Std 1003.1-2001 does not permit  this  behavior.
       Historically,  the C, S, and s commands did not copy replaced text into
       the numeric buffers. For consistency and simplicity  of  specification,
       IEEE Std 1003.1-2001  requires that they behave like their respective c
       commands in all respects.

   Delete
       Historically, lines in open mode that were deleted  were  scrolled  up,
       and  an  @ glyph written over the beginning of the line. In the case of
       terminals that are incapable  of  the  necessary  cursor  motions,  the
       editor  erased  the  deleted line from the screen. IEEE Std 1003.1-2001
       requires conformance to historical practice; that is, if  the  terminal
       cannot display the '@' character, the line cannot remain on the screen.

   Delete to End-of-Line
       Some  historical  implementations  of  the  D command did not behave as
       described by IEEE Std 1003.1-2001 when the $ key was  remapped  because
       they  were  implemented  by  pushing the $ key onto the input queue and
       reprocessing it.  IEEE Std 1003.1-2001 does not permit this behavior.

   Join
       An historical oddity of vi is that the commands J, 1J, and 2J  are  all
       equivalent.   IEEE Std 1003.1-2001  requires  conformance to historical
       practice.  The vi J command is  specified  in  terms  of  the  ex  join
       command  with  an  ex command count value. The address correction for a
       count that is past  the  end  of  the  edit  buffer  is  necessary  for
       historical compatibility for both ex and vi.

   Mark Position
       Historical  practice  is that only lowercase letters, plus '`' and '" ,
       could be used to mark a cursor position. IEEE Std 1003.1-2001  requires
       conformance  to  historical practice, but encourages implementations to
       support other characters as marks as well.

   Repeat Regular Expression Find (Forward and Reverse)
       Historically, the N  and  n  commands  could  not  be  used  as  motion
       components  for  the  c  command. With the exception of the cN command,
       which worked if the search crossed a line  boundary,  the  text  region
       would  be  discarded, and the user would not be in text input mode. For
       consistency and simplicity of specification, IEEE Std 1003.1-2001  does
       not permit this behavior.

   Insert Empty Line (Below and Above)
       Historically, counts to the O and o commands were used as the number of
       physical lines to open, if the  terminal  was  dumb  and  the  slowopen
       option  was  not  set.  This was intended to minimize traffic over slow
       connections and repainting  for  dumb  terminals.  IEEE Std 1003.1-2001
       does  not  permit  this  behavior,  requiring  that a count to the open
       command behave as  for  other  text  input  commands.  This  change  to
       historical practice was made for consistency, and because a superset of
       the functionality is provided by the slowopen edit option.

   Put from Buffer (Following and Before)
       Historically, counts to the p and P commands were ignored if the buffer
       was  a  line mode buffer, but were (mostly) implemented as described in
       IEEE Std 1003.1-2001 if the buffer was a character mode buffer. Because
       implementations  exist  that  do  not have this limitation, and because
       pasting lines multiple times is generally useful,  IEEE Std 1003.1-2001
       requires that count be supported for all p and P commands.

       Historical  implementations  of  vi  were  widely  known  to have major
       problems in the p and P commands, particularly when unusual regions  of
       text  were  copied into the edit buffer. The standard developers viewed
       these  as  bugs,  and  they  are  not  permitted  for  consistency  and
       simplicity of specification.

       Historically, a P or p command (or an ex put command executed from open
       or visual mode) executed in an empty file, left an empty  line  as  the
       first   line   of   the   file.   For  consistency  and  simplicity  of
       specification, IEEE Std 1003.1-2001 does not permit this behavior.

   Replace Character
       Historically, the r command did not correctly handle the erase and word
       erase  characters  as  arguments, nor did it handle an associated count
       greater than 1 with a <carriage-return> argument, for which it replaced
       count characters with a single <newline>. IEEE Std 1003.1-2001 does not
       permit these inconsistencies.

       Historically, the r  command  permitted  the  <control>-V  escaping  of
       entered  characters,  such as <ESC> and the <carriage-return>; however,
       it  required  two  leading  <control>-V  characters  instead  of   one.
       IEEE Std 1003.1-2001 requires that this be changed for consistency with
       the other text input commands of vi.

       Historically, it is an error to enter the r command if there  are  less
       than  count  characters  at  or  after  the cursor in the line. While a
       reasonable and unambiguous extension would be to permit the  r  command
       on  empty lines, it would require that too large a count be adjusted to
       match the number of characters at or after the cursor for  consistency,
       which is sufficiently different from historical practice to be avoided.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

   Replace Characters
       Historically, if there were autoindent characters in the line on  which
       the  R  command  was  run,  and autoindent was set, the first <newline>
       would be properly indented and no characters would be replaced  by  the
       <newline>.  Each additional <newline> would replace n characters, where
       n was the number of characters that were needed to indent the  rest  of
       the line to the proper indentation level. This behavior is a bug and is
       not permitted by IEEE Std 1003.1-2001.

   Undo
       Historical practice for cursor positioning after undoing  commands  was
       mixed.  In  most  cases,  when  undoing commands that affected a single
       line, the cursor was moved to the start of added or  changed  text,  or
       immediately after deleted text. However, if the user had moved from the
       line being changed, the  column  was  either  set  to  the  first  non-
       <blank>,  returned to the origin of the command, or remained unchanged.
       When undoing commands that affected multiple lines or entire lines, the
       cursor  was moved to the first character in the first line restored. As
       an example of how inconsistent this was, a search,  followed  by  an  o
       text  input command, followed by an undo would return the cursor to the
       location where the o command was entered, but a cw command followed  by
       an  o  command followed by an undo would return the cursor to the first
       non- <blank> of the line. IEEE Std 1003.1-2001 requires the most useful
       of  these  behaviors, and discards the least useful, in the interest of
       consistency and simplicity of specification.

   Yank
       Historically, the yank command did not move to the end of the motion if
       the  motion  was  in  the forward direction. It moved to the end of the
       motion if the motion was in the backward direction, except  for  the  _
       command,  or for the G and ' commands when the end of the motion was on
       the current line.  This was further complicated by the fact that for  a
       number  of  motion  commands, the yank command moved the cursor but did
       not update the screen; for example, a subsequent command would move the
       cursor from the end of the motion, even though the cursor on the screen
       had  not  reflected  the  cursor  movement  for   the   yank   command.
       IEEE Std 1003.1-2001  requires  that  all yank commands associated with
       backward motions  move  the  cursor  to  the  end  of  the  motion  for
       consistency, and specifically, to make ' commands as motions consistent
       with search patterns as motions.

   Yank Current Line
       Some historical implementations of the Y  command  did  not  behave  as
       described by IEEE Std 1003.1-2001 when the '_' key was remapped because
       they were implemented by pushing the '_' key onto the input  queue  and
       reprocessing it. IEEE Std 1003.1-2001 does not permit this behavior.

   Redraw Window
       Historically, the z command always redrew the screen. This is permitted
       but not required by IEEE Std 1003.1-2001, because of the  frequent  use
       of  the  z  command in macros such as map n nz. for screen positioning,
       instead of its use to change the screen size. The  standard  developers
       believed  that  expanding  or  scrolling  the  screen  offered a better
       interface for users. The ability to redraw the screen is  preserved  if
       the  optional  new window size is specified, and in the <control>-L and
       <control>-R commands.

       The semantics of z^ are confusing at best. Historical practice is  that
       the  screen  before  the  screen  that ended with the specified line is
       displayed.  IEEE Std 1003.1-2001  requires  conformance  to  historical
       practice.

       Historically, the z command would not display a partial line at the top
       or bottom of the screen. If the partial line would normally  have  been
       displayed  at  the  bottom  of  the screen, the command worked, but the
       partial line was replaced with '@'  characters.  If  the  partial  line
       would  normally  have  been  displayed  at  the  top of the screen, the
       command would fail.  For consistency and simplicity  of  specification,
       IEEE Std 1003.1-2001 does not permit this behavior.

       Historically,  the z command with a line specification of 1 ignored the
       command.   For   consistency   and   simplicity    of    specification,
       IEEE Std 1003.1-2001 does not permit this behavior.

       Historically,  the z command did not set the cursor column to the first
       non- <blank> for the character if the first screen was to be displayed,
       and   was   already   displayed.  For  consistency  and  simplicity  of
       specification, IEEE Std 1003.1-2001 does not permit this behavior.

   Input Mode Commands in vi
       Historical implementations of vi did not permit the user to erase  more
       than  a single line of input, or to use normal erase characters such as
       line erase, worderase, and erase to  erase  autoindent  characters.  As
       there  exist  implementations of vi that do not have these limitations,
       both behaviors are permitted, but only historical practice is required.
       In  the  case  of  these  extensions,  vi  is  required to pause at the
       autoindent and previous line boundaries.

       Historical implementations of vi updated only the portion of the screen
       where  the  current  cursor  character  was  displayed.   For  example,
       consider the vi input keystrokes:

              iabcd<escape>0C<tab>

       Historically, the <tab> would overwrite the characters "abcd"  when  it
       was  displayed.  Other  implementations  replace only the 'a' character
       with the <tab>, and then push the rest of the characters ahead  of  the
       cursor.    Both   implementations   have   problems.   The   historical
       implementation is  probably  visually  nicer  for  the  above  example;
       however, for the keystrokes:

              iabcd<ESC>0R<tab><ESC>

       the  historical implementation results in the string "bcd" disappearing
       and then magically reappearing when the  <ESC>  character  is  entered.
       IEEE Std 1003.1-2001  requires  the  former  behavior  when overwriting
       erase-columns-that  is,  overwriting  characters  that  are  no  longer
       logically part of the edit buffer-and the latter behavior otherwise.

       Historical   implementations   of  vi  discarded  the  <control>-D  and
       <control>-T characters when they were entered  at  places  where  their
       command   functionality   was   not  appropriate.  IEEE Std 1003.1-2001
       requires that the <control>-T functionality always  be  available,  and
       that  <control>-D  be  treated  as  any other key when not operating on
       autoindent characters.

   NUL
       Some historical implementations of vi limited the number of  characters
       entered    using    the    NUL    input   character   to   256   bytes.
       IEEE Std 1003.1-2001 permits this limitation; however,  implementations
       are encouraged to remove this limit.

   <control>-D
       See  also  Rationale  for  the input mode command <newline>. The hidden
       assumptions in the  <control>-D  command  (and  in  the  vi  autoindent
       specification  in  general) is that <space>s take up a single column on
       the screen and that <tab>s are  comprised  of  an  integral  number  of
       <space>s.

   <newline>
       Implementations  are  permitted to rewrite autoindent characters in the
       line when <newline>, <carriage-return>,  <control>-D,  and  <control>-T
       are  entered,  or  when the shift commands are used, because historical
       implementations have both done so and found it necessary to do so.  For
       example,  a  <control>-D when the cursor is preceded by a single <tab>,
       with tabstop set to 8, and shiftwidth set to  3,  will  result  in  the
       <tab> being replaced by several <space>s.

   <control>-T
       See   also   the  Rationale  for  the  input  mode  command  <newline>.
       Historically, <control>-T only worked if no non- <blank>s had yet  been
       input  in  the current input line. In addition, the characters inserted
       by <control>-T were treated as autoindent characters, and could not  be
       erased  using  normal  user  erase  characters. Because implementations
       exist that do not have these limitations, and as  moving  to  a  column
       boundary  is  generally useful, IEEE Std 1003.1-2001 requires that both
       limitations be removed.

   <control>-V
       Historically, vi used ^V, regardless of the value of  the  literal-next
       character  of  the terminal.  IEEE Std 1003.1-2001 requires conformance
       to historical practice.

       The uses described  for  <control>-V  can  also  be  accomplished  with
       <control>-Q,  which is useful on terminals that use <control>-V for the
       down-arrow  function.  However,  most  historical  implementations  use
       <control>-Q  for  the  termios  START  character,  so  the  editor will
       generally not receive the <control>-Q unless stty ixon mode is  set  to
       off. (In addition, some historical implementations of vi explicitly set
       ixon mode to on, so it was difficult for the user to set  it  to  off.)
       Any  of the command characters described in IEEE Std 1003.1-2001 can be
       made ineffective by their  selection  as  termios  control  characters,
       using  the  stty  utility  or  other  methods  described  in the System
       Interfaces volume of IEEE Std 1003.1-2001.

   <ESC>
       Historically, SIGINT alerted the terminal when used to end input  mode.
       This behavior is permitted, but not required, by IEEE Std 1003.1-2001.

FUTURE DIRECTIONS

       None.

SEE ALSO

       ed , ex , stty

COPYRIGHT

       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.php .



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