вернуть строку, описывающую номер ошибки (return string describing error number)
Имя (Name)
strerror, strerrorname_np, strerrordesc_np, strerror_r,
strerror_l - return string describing error number
Синопсис (Synopsis)
#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_t buflen);
/* XSI-compliant */
char *strerror_r(int errnum, char *buf, 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.
Описание (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.
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".
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').
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.
Возвращаемое значение (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.
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 (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.
Ошибки (Error)
EINVAL The value of errnum is not a valid error number.
ERANGE Insufficient storage was supplied to contain the error
description string.
Версии (Versions)
The strerror_l() function first appeared in glibc 2.6.
The strerrorname_np() and strerrordesc_np() functions first
appeared in glibc 2.32.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────────┬───────────────┬────────────────────────────┐
│Interface │ Attribute │ Value │
├───────────────────┼───────────────┼────────────────────────────┤
│strerror() │ Thread safety │ MT-Unsafe race:strerror │
├───────────────────┼───────────────┼────────────────────────────┤
│strerrorname_np(), │ Thread safety │ MT-Safe │
│strerrordesc_np() │ │ │
├───────────────────┼───────────────┼────────────────────────────┤
│strerror_r(), │ Thread safety │ MT-Safe │
│strerror_l() │ │ │
└───────────────────┴───────────────┴────────────────────────────┘
Стандарты (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 functions strerror_r(), strerrorname_np(), and
strerrordesc_np() are nonstandard extensions.
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.
Примечание (Note)
The GNU C Library uses a buffer of 1024 characters for
strerror(). This buffer size therefore should be sufficient to
avoid an ERANGE error when calling strerror_r().
strerrorname_np() and strerrordesc_np() are thread-safe and
async-signal-safe.
Смотри также (See also)
err(3), errno(3), error(3), perror(3), strsignal(3), locale(7)
