Name
strerror, strerror_r, strerror_l — 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 */
char
*strerror_l( |
int errnum, |
locale_t locale); |
![[Note]](../stylesheet/note.png) |
Note | ||||
|---|---|---|---|---|---|
|
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. (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.
strerror_r()
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
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_C_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
errnum is unknown).
The string always includes a terminating null byte
('\0').
RETURN VALUE
The strerror(), strerror_l(), 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, 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 strerror() 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.
ERRORS
- EINVAL
-
The value of
errnumis not a valid error number. - ERANGE
-
Insufficient storage was supplied to contain the error description string.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
strerror() |
Thread safety | MT-Unsafe race:strerror |
|
|
Thread safety | MT-Safe |
CONFORMING TO
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
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. C99
and POSIX.1-2008 require the return value to be non-NULL.
COLOPHON
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (C) 1993 David Metcalfe (davidprism.demon.co.uk) and Copyright (C) 2005, 2014 Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END References consulted: Linux libc source code Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) 386BSD man pages Modified Sat Jul 24 18:05:30 1993 by Rik Faith <faithcs.unc.edu> Modified Fri Feb 16 14:25:17 1996 by Andries Brouwer <aebcwi.nl> Modified Sun Jul 21 20:55:44 1996 by Andries Brouwer <aebcwi.nl> Modified Mon Oct 15 21:16:25 2001 by John Levon <mozcompsoc.man.ac.uk> Modified Tue Oct 16 00:04:43 2001 by Andries Brouwer <aebcwi.nl> Modified Fri Jun 20 03:04:30 2003 by Andries Brouwer <aebcwi.nl> 2005-12-13, mtk, Substantial rewrite of strerror_r() description Addition of extra material on portability and standards. |