STRERROR(3C) Standard C Library Functions STRERROR(3C)

NAME

strerror, strerror_r, strerror_l, strerrordesc_np, strerrorname_np -
get error message string

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <string.h>

char *
strerror(int errnum);

int
strerror_r(int errnum, char *strerrbuf, size_t buflen);

char *
strerror_l(int errnum, locale_t loc);

const char *
strerrordesc_np(int errnum);

const char *
strerrorname_np(int errnum);

DESCRIPTION

The strerror() function maps the error number in errnum to an error
message string, and returns a pointer to that string. It uses the same
set of error messages as perror(3C). The returned string should not be
overwritten. The string will be translated based on the current
locale.

The strerror_r() function maps the error number in errnum to an error
message string and returns the string in the buffer pointed to by
strerrbuf with length buflen.

The strerror_l() function maps the error number in errnum to an error
message string in the locale indicated by loc. The returned string
should not be overwritten. If loc is passed the NULL pointer, then the
locale of the calling thread's current locale will be used instead,
like strerror().

Because the strerror() and strerror_l() functions, return localized
strings in the event of an unknown error, one must use the value of
errno to detect an error. Callers should first set errno to 0 before
the call to either function and then check the value of errno after the
call. If the value of errno is non-zero then an error has occurred.

The strerrordesc_np() function behaves the same as strerror(), but will
always return the error message string in the C locale and will not
provide a translate message. Unlike strerror(), unknown error messages
will return a NULL pointer. Clearing errno prior to calling
strerrordesc_np() is still advised, as with strerror().

The strerrorname_np() function translates errnum into the string name
of the error constant. For example: "EIO", "EINTR", etc. When passed
the value of 0, there is no traditional error string. To match
originating implementations, the string "0" is returned in that case.

RETURN VALUES

Upon successful completion, strerror() and strerror_l() return a
pointer to the generated message string. Otherwise, they set errno and
returns a pointer to an error message string. They return the
localized string "Unknown error" if errnum is not a valid error number.

Upon successful completion, strerror_r() returns 0. Otherwise it sets
errno and returns the value of errno to indicate the error. It returns
the localized string "Unknown error" in the buffer pointed to by
strerrbuf if errnum is not a valid error number.

Upon successful completion, the strerrordesc_np() function returns the
C locale's generated message string. Otherwise, NULL is returned and
errno is set. Unlike strerror(), this occurs when a string's
translation is not known.

Upon successful completion, the strerrorname_np() function returns the
C language constant name of the error. Otherwise, NULL is returned and
errno is set.

ERRORS

These functions may fail if:

EINVAL The value of errnum is not a valid error number.

The strerror_r() function may fail if:

ERANGE The buflen argument specifies insufficient storage
to contain the generated message string.

USAGE

Messages returned from these functions (other than strerrordesc_np()
and strerrorname_np()) are in the native language specified by the
LC_MESSAGES locale category. See setlocale(3C) and uselocale(3C).

INTERFACE STABILITY

Committed

MT-LEVEL
Safe

SEE ALSO

gettext(3C), perror(3C), setlocale(3C), uselocale(3C), attributes(7),
standards(7)

illumos April 6, 2024 illumos