man/man3c/strerror.3c

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 STRERROR 3C "Aug 17, 2015"
 NAME
strerror, strerror_r, strerror_l - get error message string
 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);

 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 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.

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.
 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.
 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 are in the native language specified by
the LC_MESSAGES locale category. See setlocale(3C) and
uselocale(3C).
 ATTRIBUTES

See attributes(5) for descriptions of the following attributes:


ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Standard
MT-Level Safe


 SEE ALSO

gettext(3C), perror(3C), setlocale(3C), uselocale(3C),
attributes(5), standards(5)