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, possi-
       bly using the LC_MESSAGES part of the current locale to select the appropriate language.  This string must not  be  modi-
       fied  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-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 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 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, strerror() 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)