strerror, strerror_r — return string describing error number
#include <string.h>
char
*strerror( |
int | errnum) ; |
char
*strerror_r( |
int | errnum, |
char * | buf, | |
size_t | buflen) ; |
/* GNU-specific strerror_r() */ #define _XOPEN_SOURCE 600 #include <string.h>
int
strerror_r( |
int | errnum, |
char * | buf, | |
size_t | buflen) ; |
/* XSI-compliant strerror_r() */
The strerror
() function
returns a string describing 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, and a
GNU-specific version (available since glibc 2.0). If
_XOPEN_SOURCE is defined with the value 600, then the
XSI-compliant version is provided, otherwise the GNU-specific
version is provided.
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.
The strerror
() and
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.
The value of errnum
is not a valid
error number.
Insufficient storage was supplied to contain the error description string.
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 non-standard
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.
err(3), errno(3), error(3), perror(3), strsignal(3), feature_test_macros(7)
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