file — determine file type
file [-bcEhiklLNnprsvz0] [--apple] [--mime-encoding] [--mime-type]
[-e testname] [-F separator] [-f namefile] [-m magicfiles] file ...
file -C [-m magicfiles]
This manual page documents version 5.19 of the file command.
file tests each argument in an attempt to classify it. There are three
sets of tests, performed in this order: filesystem tests, magic tests,
and language tests. The first test that succeeds causes the file type to
The type printed will usually contain one of the words text (the file
contains only printing characters and a few common control characters and
is probably safe to read on an ASCII terminal), executable (the file
contains the result of compiling a program in a form understandable to
some UNIX kernel or another), or data meaning anything else (data is
usually “binary” or non-printable). Exceptions are well-known file
formats (core files, tar archives) that are known to contain binary data.
When adding local definitions to /etc/magic, make sure to preserve these
keywords. Users depend on knowing that all the readable files in a
directory have the word “text” printed. Don't do as Berkeley did and
change “shell commands text” to “shell script”.
The filesystem tests are based on examining the return from a stat(2)
system call. The program checks to see if the file is empty, or if it's
some sort of special file. Any known file types appropriate to the
system you are running on (sockets, symbolic links, or named pipes
(FIFOs) on those systems that implement them) are intuited if they are
defined in the system header file <sys/stat.h>.
The magic tests are used to check for files with data in particular fixed
formats. The canonical example of this is a binary executable (compiled
program) a.out file, whose format is defined in <elf.h>, <a.out.h> and
possibly <exec.h> in the standard include directory. These files have a
“magic number” stored in a particular place near the beginning of the
file that tells the UNIX operating system that the file is a binary
executable, and which of several types thereof. The concept of a “magic”
has been applied by extension to data files. Any file with some
invariant identifier at a small fixed offset into the file can usually be
described in this way. The information identifying these files is read
from /etc/magic and the compiled magic file /usr/share/misc/magic.mgc, or
the files in the directory /usr/share/misc/magic if the compiled file
does not exist. In addition, if $HOME/.magic.mgc or $HOME/.magic exists,
it will be used in preference to the system magic files.
If a file does not match any of the entries in the magic file, it is
examined to see if it seems to be a text file. ASCII, ISO-8859-x, non-
ISO 8-bit extended-ASCII character sets (such as those used on Macintosh
and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and
EBCDIC character sets can be distinguished by the different ranges and
sequences of bytes that constitute printable text in each set. If a file
passes any of these tests, its character set is reported. ASCII,
ISO-8859-x, UTF-8, and extended-ASCII files are identified as “text”
because they will be mostly readable on nearly any terminal; UTF-16 and
EBCDIC are only “character data” because, while they contain text, it is
text that will require translation before it can be read. In addition,
file will attempt to determine other characteristics of text-type files.
If the lines of a file are terminated by CR, CRLF, or NEL, instead of the
Unix-standard LF, this will be reported. Files that contain embedded
escape sequences or overstriking will also be identified.
Once file has determined the character set used in a text-type file, it
will attempt to determine in what language the file is written. The
language tests look for particular strings (cf. <names.h>) that can
appear anywhere in the first few blocks of a file. For example, the
keyword .br indicates that the file is most likely a troff(1) input file,
just as the keyword struct indicates a C program. These tests are less
reliable than the previous two groups, so they are performed last. The
language test routines also test for some miscellany (such as tar(1)
Any file that cannot be identified as having been written in any of the
character sets listed above is simply said to be “data”.
Causes the file command to output the file type and creator code
as used by older MacOS versions. The code consists of eight
letters, the first describing the file type, the latter the
Do not prepend filenames to output lines (brief mode).
Write a magic.mgc output file that contains a pre-parsed version
of the magic file or directory.
Cause a checking printout of the parsed form of the magic file.
This is usually used in conjunction with the -m flag to debug a
new magic file before installing it.
-E On filesystem errors (file not found etc), instead of handling
the error as regular output as POSIX mandates and keep going,
issue an error message and exit.
-e, --exclude testname
Exclude the test named in testname from the list of tests made to
determine the file type. Valid test names are:
apptype EMX application type (only on EMX).
ascii Various types of text files (this test will try to
guess the text encoding, irrespective of the setting of
the ‘encoding’ option).
encoding Different text encodings for soft magic tests.
tokens Ignored for backwards compatibility.
cdf Prints details of Compound Document Files.
compress Checks for, and looks inside, compressed files.
elf Prints ELF file details.
soft Consults magic files.
tar Examines tar files.
-F, --separator separator
Use the specified string as the separator between the filename
and the file result returned. Defaults to ‘:’.
-f, --files-from namefile
Read the names of the files to be examined from namefile (one per
line) before the argument list. Either namefile or at least one
filename argument must be present; to test the standard input,
use ‘-’ as a filename argument. Please note that namefile is
unwrapped and the enclosed filenames are processed when this
option is encountered and before any further options processing
is done. This allows one to process multiple lists of files with
different command line arguments on the same file invocation.
Thus if you want to set the delimiter, you need to do it before
you specify the list of files, like: “-F @ -f namefile”, instead
of: “-f namefile -F @”.
option causes symlinks not to be followed (on systems that
support symbolic links). This is the default if the environment
variable POSIXLY_CORRECT is not defined.
Causes the file command to output mime type strings rather than
the more traditional human readable ones. Thus it may say
‘text/plain; charset=us-ascii’ rather than “ASCII text”.
Like -i, but print only the specified element(s).
Don't stop at the first match, keep going. Subsequent matches
will be have the string ‘
- ’ prepended. (If you want a
newline, see the -r option.) The magic pattern with the highest
strength (see the -l option) comes first.
Shows a list of patterns and their strength sorted descending by
magic(4) strength which is used for the matching (see also the -k
option causes symlinks to be followed, as the like-named option
in ls(1) (on systems that support symbolic links). This is the
default if the environment variable POSIXLY_CORRECT is defined.
-m, --magic-file magicfiles
Specify an alternate list of files and directories containing
magic. This can be a single item, or a colon-separated list. If
a compiled magic file is found alongside a file or directory, it
will be used instead.
Don't pad filenames so that they align in the output.
Force stdout to be flushed after checking each file. This is
only useful if checking a list of files. It is intended to be
used by programs that want filetype output from a pipe.
On systems that support utime(3) or utimes(2), attempt to
preserve the access time of files analyzed, to pretend that file
never read them.
Don't translate unprintable characters to \ooo. Normally file
translates unprintable characters to their octal representation.
Normally, file only attempts to read and determine the type of
argument files which stat(2) reports are ordinary files. This
prevents problems, because reading special files may have
peculiar consequences. Specifying the -s option causes file to
also read argument files which are block or character special
files. This is useful for determining the filesystem types of
the data in raw disk partitions, which are block special files.
This option also causes file to disregard the file size as
reported by stat(2) since on some systems it reports a zero size
for raw disk partitions.
Print the version of the program and exit.
Try to look inside compressed files.
Output a null character ‘