STRERROR(3) Linux Programmer's Manual STRERROR(3)NAME
strerror, strerror_r - return string describing error number
SYNOPSIS
#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() */
DESCRIPTION
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 sub‐
sequent call to perror() or strerror(). No library function will mod‐
ify 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.
RETURN VALUE
The strerror() and strerror_r() functions return the appropriate error
description string, or an "Unknown error nnn" message if the error num‐
ber 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.
ERRORS
EINVAL The value of errnum is not a valid error number.
ERANGE Insufficient storage was supplied to contain the error descrip‐
tion string.
CONFORMING TO
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 func‐
tion result in the event of an error. On some systems, strerror()
returns NULL if the error number is unknown. On other systems, str‐
error() returns a string something like "Error nnn occurred" and sets
errno to EINVAL if the error number is unknown.
SEE ALSOerr(3), errno(3), error(3), perror(3), strsignal(3)
2005-12-13 STRERROR(3)
