STRERROR(3)						     Linux Programmer's Manual						       STRERROR(3)

NAME

       strerror, strerror_r - 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 */

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

       The XSI-compliant version of strerror_r() 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.  This string must not be modified by the application, but may be
       modified by a subsequent call to perror(3) or strerror().  No library function will modify this string.

       The  strerror_r() function is similar to strerror(), but is thread safe.  This function is available in two versions: an XSI-compliant ver-
       sion specified in POSIX.1-2001 (available since glibc 2.3.4), 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 the string always includes  a  termi-
       nating null byte.

RETURN VALUE

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

       The XSI-compliant strerror_r() function returns 0 on success; on error, -1 is returned and errno is set to indicate the error.

ERRORS

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

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

CONFORMING TO

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

       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, str-
       error() returns a string something like "Error nnn occurred" and sets errno to EINVAL if the error number is unknown.

SEE ALSO

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

COLOPHON

       This page is part of release 3.25 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/.

								    2009-03-30							       STRERROR(3)