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NAME

       strerror,  strerror_r,  strerror_l  -  return  string  describing error
       number

SYNOPSIS

       #include <string.h>

       char *strerror(int errnum);

       int strerror_r(int errnum, char *buf, size_t buflen);
                   /* XSI-compliant */

       char *strerror_r(int errnum, char *buf, size_t buflen);
                   /* GNU-specific */

       char *strerror_l(int errnum, locale_t locale);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       strerror_r():
           The XSI-compliant version is provided if:
           (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) &&
           ! _GNU_SOURCE
           Otherwise, the GNU-specific version is provided.

DESCRIPTION

       The  strerror()  function  returns a pointer to a string that describes
       the error code passed  in  the  argument  errnum,  possibly  using  the
       LC_MESSAGES  part  of  the  current  locale  to  select the appropriate
       language.  (For example, if errnum is EINVAL, the returned  description
       will  be  "Invalid argument".)  This string must not be modified by the
       application, but may be modified by a subsequent call to strerror()  or
       strerror_l().   No  other  library  function, including perror(3), will
       modify this string.

   strerror_r()
       The strerror_r() function is similar to strerror(), but is thread safe.
       This  function  is  available in two versions: an XSI-compliant version
       specified in POSIX.1-2001 (available since glibc 2.3.4, but not  POSIX-
       compliant  until  glibc  2.13),  and  a GNU-specific version (available
       since glibc 2.0).  The  XSI-compliant  version  is  provided  with  the
       feature  test macros settings shown in the SYNOPSIS; otherwise the GNU-
       specific version is provided.  If no feature test macros are explicitly
       defined,  then  (since  glibc  2.4) _POSIX_SOURCE is defined by default
       with  the  value  200112L,  so  that  the  XSI-compliant   version   of
       strerror_r() is provided by default.

       The  XSI-compliant strerror_r() is preferred for portable applications.
       It returns the error string in the user-supplied buffer buf  of  length
       buflen.

       The  GNU-specific strerror_r() returns a pointer to a string containing
       the error message.  This may be either a pointer to a string  that  the
       function  stores in buf, or a pointer to some (immutable) static string
       (in which case buf is unused).  If the function stores a string in buf,
       then  at  most  buflen bytes are stored (the string may be truncated if
       buflen is too small and errnum is unknown).  The string always includes
       a terminating null byte ('').

   strerror_l()
       strerror_l()  is like strerror(), but maps errnum to a locale-dependent
       error message in the locale  specified  by  locale.   The  behavior  of
       strerror_l()  is  undefined  if  locale  is  the  special locale object
       LC_GLOBAL_LOCALE or is not a valid locale object handle.

RETURN VALUE

       The  strerror(),  strerror_l(),  and  the   GNU-specific   strerror_r()
       functions  return  the  appropriate  error  description  string,  or an
       "Unknown error nnn" message if the error number is unknown.

       The XSI-compliant strerror_r()  function  returns  0  on  success.   On
       error,  a (positive) error number is returned (since glibc 2.13), or -1
       is returned and errno is set to  indicate  the  error  (glibc  versions
       before 2.13).

       POSIX.1-2001  and  POSIX.1-2008  require  that  a  successful  call  to
       strerror() or strerror_l() shall leave errno unchanged, and note  that,
       since  no  function  return  value is reserved to indicate an error, an
       application that wishes to check for errors should initialize errno  to
       zero before the call, and then check errno after the call.

ERRORS

       EINVAL The value of errnum is not a valid error number.

       ERANGE Insufficient   storage   was   supplied  to  contain  the  error
              description string.

ATTRIBUTES

   Multithreading (see pthreads(7))
       The strerror() function is not thread-safe.

       The strerror_r() function is thread-safe.

VERSIONS

       The strerror_l() function first appeared in glibc 2.6.

CONFORMING TO

       strerror() is specified by POSIX.1-2001, POSIX.1-2008,  C89,  and  C99.
       strerror_r() is specified by POSIX.1-2001 and POSIX.1-2008.

       strerror_l() is specified in POSIX.1-2008.

       The GNU-specific strerror_r() function is a nonstandard extension.

       POSIX.1-2001  permits strerror() to set errno if the call encounters an
       error, but does not specify  what  value  should  be  returned  as  the
       function  result in the event of an error.  On some systems, strerror()
       returns NULL if  the  error  number  is  unknown.   On  other  systems,
       strerror()  returns  a  string  something like "Error nnn occurred" and
       sets errno  to  EINVAL  if  the  error  number  is  unknown.   C99  and
       POSIX.1-2008 require the return value to be non-NULL.

SEE ALSO

       err(3), errno(3), error(3), perror(3), strsignal(3), locale(7)

COLOPHON

       This  page  is  part of release 3.65 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

                                  2014-03-18                       STRERROR(3)



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