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

       strerror,  strerror_r, strerror_l - return string describing error num-

       #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 */

       char *strerror_l(int errnum, locale_t locale);

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

           The XSI-compliant version is provided if:
           (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) &&
           ! _GNU_SOURCE
           Otherwise, the GNU-specific version is provided.

       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.  (For example, if errnum is  EINVAL,  the  returned  description
       will  be  "Invalid argument".)  This string must not be modified by the
       application, but may be modified by a subsequent call to strerror()  or
       strerror_l().   No  other  library  function, including perror(3), 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, but not  POSIX-
       compliant  until  glibc  2.13),  and  a GNU-specific version (available
       since glibc 2.0).  The XSI-compliant version is provided with the  fea-
       ture test macros settings shown in the SYNOPSIS; otherwise the GNU-spe-
       cific 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  str-
       error_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

       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 errnum is unknown).  The string always includes
       a terminating null byte ('\0').

       strerror_l()  is like strerror(), but maps errnum to a locale-dependent
       error message in the locale specified by locale.  The behavior of  str-
       error_l()   is  undefined  if  locale  is  the  special  locale  object
       LC_GLOBAL_LOCALE or is not a valid locale object handle.

       The strerror(), strerror_l(), and the GNU-specific  strerror_r()  func-
       tions  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,  a (positive) error number is returned (since glibc 2.13), or -1
       is returned and errno is set to  indicate  the  error  (glibc  versions
       before 2.13).

       POSIX.1-2001  and  POSIX.1-2008  require that a successful call to str-
       error() or strerror_l() shall leave errno  unchanged,  and  note  that,
       since  no  function  return  value is reserved to indicate an error, an
       application that wishes to check for errors should initialize errno  to
       zero before the call, and then check errno after the call.

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

       ERANGE Insufficient  storage was supplied to contain the error descrip-
              tion string.

       For  an  explanation  of  the  terms  used   in   this   section,   see

       |Interface      | Attribute     | Value                   |
       |strerror()     | Thread safety | MT-Unsafe race:strerror |
       |strerror_r(),  | Thread safety | MT-Safe                 |
       |strerror_l()   |               |                         |
       The strerror_l() function first appeared in glibc 2.6.

       strerror()  is  specified  by POSIX.1-2001, POSIX.1-2008, C89, and C99.
       strerror_r() is specified by POSIX.1-2001 and POSIX.1-2008.

       strerror_l() is specified in POSIX.1-2008.

       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.  C99 and POSIX.1-2008
       require the return value to be non-NULL.

       err(3), errno(3), error(3), perror(3), strsignal(3), locale(7)

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                                  2015-03-02                       STRERROR(3)
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