strerror—convert error number to string #include <string.h>
char *strerror(int errnum);
char *_strerror_r(struct _reent ptr, int errnum,
int internal, int *error);
Description
strerror converts the error number errnum into a
string. The value of errnum is usually a copy of errno.
If errnum is not a known error number, the result points to an
empty string.
This implementation of strerror prints out the following strings
for each of the values defined in `errno.h':
0E2BIGEACCESEADDRINUSEEADVEAFNOSUPPORTEAGAINEALREADYEBADFEBADMSGEBUSYECHILDECOMMECONNABORTEDECONNREFUSEDEDEADLKEDESTADDRREQEEXISTEDOMEFAULTEFBIGEHOSTDOWNEHOSTUNREACHEIDRMEINPROGRESSEINTREINVALEIOEISCONNEISDIRELIBACCELIBBADELIBEXECELIBMAXELIBSCN.lib section in a.out corrupted
EMFILEEMLINKEMSGSIZEEMULTIHOPENAMETOOLONGENETDOWNENETUNREACHENFILEENODEVENOENTENOEXECENOLCKENOLINKENOMEMENOMSGENONETENOPKGENOPROTOOPTENOSPCENOSRENOSTRENOSYSENOTBLKENOTCONNENOTDIRENOTEMPTYENOTSOCKENOTSUPENOTTYENXIOEPERMEPIPEEPROTOEPROTOTYPEEPROTONOSUPPORTERANGEEREMOTEEROFSESHUTDOWNESOCKTNOSUPPORTESPIPEESRCHESRMNTETIMEETIMEDOUTETXTBSYEXDEVECANCELEDENOTRECOVERABLEEOWNERDEADESTRPIPE_strerror_r is a reentrant version of the above.
Returns
This function returns a pointer to a string. Your application must
not modify that string.
Portability
ANSI C requires strerror, but does not specify the strings used
for each error number.
Although this implementation of strerror is reentrant (depending
on _user_strerror), ANSI C declares that subsequent calls to
strerror may overwrite the result string; therefore portable
code cannot depend on the reentrancy of this subroutine.
Although this implementation of strerror guarantees a non-null
result with a NUL-terminator, some implementations return NULL
on failure. Although POSIX allows strerror to set errno
to EINVAL on failure, this implementation does not do so (unless
you provide _user_strerror).
POSIX recommends that unknown errnum result in a message
including that value, however it is not a requirement and this
implementation does not provide that information (unless you
provide _user_strerror).
This implementation of strerror provides for user-defined
extensibility. errno.h defines __ELASTERROR, which can be
used as a base for user-defined error values. If the user supplies a
routine named _user_strerror, and errnum passed to
strerror does not match any of the supported values,
_user_strerror is called with three arguments. The first is of
type int, and is the errnum value unknown to strerror.
The second is of type int, and matches the internal argument
of _strerror_r; this should be zero if called from strerror
and non-zero if called from any other function; _user_strerror can
use this information to satisfy the POSIX rule that no other
standardized function can overwrite a static buffer reused by
strerror. The third is of type int *, and matches the
error argument of _strerror_r; if a non-zero value is stored
into that location (usually EINVAL), then strerror will set
errno to that value, and the XPG variant of strerror_r will
return that value instead of zero or ERANGE. _user_strerror
returns a char * value; returning NULL implies that the user
function did not choose to handle errnum. The default
_user_strerror returns NULL for all input values. Note that
_user_sterror must be thread-safe, and only denote errors via the
third argument rather than modifying errno, if strerror and
strerror_r are are to comply with POSIX.
strerror requires no supporting OS subroutines.