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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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strerror(3) Library Functions Manual strerror(3)
strerror, strerrorname_np, strerrordesc_np, strerror_r,
strerror_l - return string describing error number
Standard C library (libc, -lc)
#include <string.h>
char *strerror(int errnum);
const char *strerrorname_np(int errnum);
const char *strerrordesc_np(int errnum);
int strerror_r(int errnum, char buf[.buflen], size_t buflen);
/* XSI-compliant */
char *strerror_r(int errnum, char buf[.buflen], size_t buflen);
/* GNU-specific */
char *strerror_l(int errnum, locale_t locale);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
strerrorname_np(), strerrordesc_np():
_GNU_SOURCE
strerror_r():
The XSI-compliant version is provided if:
(_POSIX_C_SOURCE >= 200112L) && ! _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. (For example, if errnum is EINVAL, the
returned description will be "Invalid argument".) This string
must not be modified by the application, and the returned pointer
will be invalidated on a subsequent call to strerror() or
strerror_l(), or if the thread that obtained the string exits.
No other library function, including perror(3), will modify this
string.
Like strerror(), the strerrordesc_np() function returns a pointer
to a string that describes the error code passed in the argument
errnum, with the difference that the returned string is not
translated according to the current locale.
The strerrorname_np() function returns a pointer to a string
containing the name of the error code passed in the argument
errnum. For example, given EPERM as an argument, this function
returns a pointer to the string "EPERM". Given 0 as an argument,
this function returns a pointer to the string "0".
strerror_r()
strerror_r() is like strerror(), but might use the supplied
buffer buf instead of allocating one internally. 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').
strerror_l()
strerror_l() is like strerror(), but maps errnum to a locale-
dependent error message in the locale specified by locale. The
behavior of strerror_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()
functions return the appropriate error description string, or an
"Unknown error nnn" message if the error number is unknown.
On success, strerrorname_np() and strerrordesc_np() return the
appropriate error description string. If errnum is an invalid
error number, these functions return NULL.
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 (before
glibc 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.
EINVAL The value of errnum is not a valid error number.
ERANGE Insufficient storage was supplied to contain the error
description string.
For an explanation of the terms used in this section, see
attributes(7).
┌────────────────────┬───────────────┬──────────────────────────┐
│ Interface │ Attribute │ Value │
├────────────────────┼───────────────┼──────────────────────────┤
│ strerror() │ Thread safety │ MT-Safe │
├────────────────────┼───────────────┼──────────────────────────┤
│ strerrorname_np(), │ Thread safety │ MT-Safe │
│ strerrordesc_np() │ │ │
├────────────────────┼───────────────┼──────────────────────────┤
│ strerror_r(), │ Thread safety │ MT-Safe │
│ strerror_l() │ │ │
└────────────────────┴───────────────┴──────────────────────────┘
Before glibc 2.32, strerror() is not MT-Safe.
strerror()
C11, POSIX.1-2008.
strerror_r()
strerror_l()
POSIX.1-2008.
strerrorname_np()
strerrordesc_np()
GNU.
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.
strerror()
POSIX.1-2001, C89.
strerror_r()
POSIX.1-2001.
strerror_l()
glibc 2.6. POSIX.1-2008.
strerrorname_np()
strerrordesc_np()
glibc 2.32.
strerrorname_np() and strerrordesc_np() are thread-safe and
async-signal-safe.
err(3), errno(3), error(3), perror(3), strsignal(3), locale(7),
signal-safety(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-06-15 strerror(3)
Pages that refer to this page: assert_perror(3), err(3), errno(3), error(3), mmv_stats_init(3), mmv_stats_registry(3), pcap_strerror(3pcap), perror(3), pmapi(3), pmerrstr(3), sd_bus_error(3), sd_bus_error_add_map(3), sd-bus-errors(3), stdio(3), strsignal(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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