STRERROR(3)		   Linux Programmers Manual		  STRERROR(3)



NAME
       strerror, strerror_r - return string describing error number

SYNOPSIS
       #include 

       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  string describing 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  sub
       sequent call to perror(3) or strerror().  No library function will mod
       ify this string.

       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), and a GNU-spe
       cific  version  (available since glibc 2.0).  The XSI-compliant version
       is provided with the feature test macros settings shown in  the	SYNOP
       SIS;  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 terminating null
       byte.

RETURN VALUE
       The strerror() 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,
       -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 descrip
	      tion 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 non-standard 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  func
       tion  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 3.05 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/.



				  2008-06-13			   STRERROR(3)