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STRERROR
Section: Linux Programmer's Manual (3)
Updated: 2009-03-30
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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 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.
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 3.27 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- SEE ALSO
-
- COLOPHON
-
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