strerror(3) - Linux manual page (original) (raw)
strerror(3) Library Functions Manual strerror(3)
NAME top
strerror, strerrorname_np, strerrordesc_np, strerror_r, strerror_l
- return string describing error numberLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#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_**[.**_size_**], size_t** _size_**);**
/* XSI-compliant */
**char *strerror_r(int** _errnum_**, char** _buf_**[.**_size_**], size_t** _size_**);**
/* 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.DESCRIPTION top
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)](../man3/perror.3.html), 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 size _size_.
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 _size_ bytes are
stored (the string may be truncated if _size_ 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.
RETURN VALUE top
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](../man3/errno.3.html)_ 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](../man3/errno.3.html)_ 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](../man3/errno.3.html)_ to zero before the call, and then check _[errno](../man3/errno.3.html)_
after the call.ERRORS top
**EINVAL** The value of _errnum_ is not a valid error number.
**ERANGE** Insufficient storage was supplied to contain the error
description string.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌────────────────────┬───────────────┬───────────────────────────┐
│ **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.STANDARDS top
**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](../man3/errno.3.html)_ 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](../man3/errno.3.html)_ to **EINVAL** if the error number
is unknown. C99 and POSIX.1-2008 require the return value to be
non-NULL.HISTORY top
**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.NOTES top
**strerrorname_np**() and **strerrordesc_np**() are thread-safe and async-
signal-safe.SEE ALSO top
[err(3)](../man3/err.3.html), [errno(3)](../man3/errno.3.html), [error(3)](../man3/error.3.html), [perror(3)](../man3/perror.3.html), [strsignal(3)](../man3/strsignal.3.html), [locale(7)](../man7/locale.7.html),
[signal-safety(7)](../man7/signal-safety.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-12-24 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)