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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 lan-
       guage.  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 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 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	 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 3.25 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)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | SEE ALSO | COLOPHON

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