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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);

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

       #define _XOPEN_SOURCE 600
       #include <string.h>

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

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() 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, and a GNU-specific version (available	 since
       glibc  2.0).   If _XOPEN_SOURCE is defined with the value 600, then the
       XSI-compliant version is provided, otherwise the	 GNU-specific  version
       is provided.

       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 strerror_r() functions return the appropriate error
       description string, or an "Unknown error nnn" message if the error num-
       ber 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
       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)



				  2005-12-13			   STRERROR(3)
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