| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | SEE ALSO | COLOPHON | The Linux Programming Interface |
STRERROR(3) Linux Programmer's Manual STRERROR(3)
strerror, strerror_r - return string describing error number
#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.
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 language. 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-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.
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.
EINVAL The value of errnum is not a valid error number.
ERANGE Insufficient storage was supplied to contain the error description
string.
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.
err(3), errno(3), error(3), perror(3), strsignal(3)
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at http://www.kernel.org/doc/man-pages/.
2009-03-30 STRERROR(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface