err(3)

NAME

err, verr, errc, verrc, errx, verrx, warn, vwarn, warnc,

vwarnc, warnx,
vwarnx, err_set_exit, err_set_file - formatted error mes

sages

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <err.h>
void
err(int eval, const char *fmt, ...);
void
err_set_exit(void (*exitf)(int));
void
err_set_file(void *vfp);
void
errc(int eval, int code, const char *fmt, ...);
void
errx(int eval, const char *fmt, ...);
void
warn(const char *fmt, ...);
void
warnc(int code, const char *fmt, ...);
void
warnx(const char *fmt, ...);
#include <stdarg.h>
void
verr(int eval, const char *fmt, va_list args);
void
verrc(int eval, int code, const char *fmt, va_list args);
void
verrx(int eval, const char *fmt, va_list args);
void
vwarn(const char *fmt, va_list args);
void
vwarnc(int code, const char *fmt, va_list args);
void
vwarnx(const char *fmt, va_list args);

DESCRIPTION

The err() and warn() family of functions display a formatted

error message on the standard error output, or on another file speci

fied using the
err_set_file() function. In all cases, the last component

of the program
name, a colon character, and a space are output. If the fmt

argument is
not NULL, the printf(3) -like formatted error message is

output. The
output is terminated by a newline character.

The err(), errc(), verr(), verrc(), warn(), warnc(),

vwarn(), and
vwarnc() functions append an error message obtained from

strerror(3)
based on a code or the global variable errno, preceded by

another colon
and space unless the fmt argument is NULL.

In the case of the errc(), verrc(), warnc(), and vwarnc()

functions, the
code argument is used to look up the error message.

The err(), verr(), warn(), and vwarn() functions use the

global variable
errno to look up the error message.

The errx() and warnx() functions do not append an error mes

sage.

The err(), verr(), errc(), verrc(), errx(), and verrx()

functions do not
return, but exit with the value of the argument eval. It is

recommended
that the standard values defined in sysexits(3) be used for

the value of
eval. The err_set_exit() function can be used to specify a

function
which is called before exit(3) to perform any necessary

cleanup; passing
a null function pointer for exitf resets the hook to do

nothing. The
err_set_file() function sets the output stream used by the

other functions. Its vfp argument must be either a pointer to an open

stream (possibly already converted to void *) or a null pointer (in

which case the
output stream is set to standard error).

EXAMPLES

Display the current errno information string and exit:

if ((p = malloc(size)) == NULL)

err(1, NULL);

if ((fd = open(file_name, O_RDONLY, 0)) == -1)

err(1, "%s", file_name);

Display an error message and exit:

if (tm.tm_hour < START_TIME)

errx(1, "too early, wait until %s",

start_time_string);

Warn of an error:

if ((fd = open(raw_device, O_RDONLY, 0)) == -1)

warnx("%s: %s: trying the block device",

raw_device, strerror(errno));

if ((fd = open(block_device, O_RDONLY, 0)) == -1)

err(1, "%s", block_device);

Warn of an error without using the global variable errno:

error = my_function(); /* returns a value from <er

rno.h> */
if (error != 0)

warnc(error, "my_function");

SEE ALSO

exit(3), fmtmsg(3), printf(3), strerror(3), sysexits(3)

HISTORY

The err() and warn() functions first appeared in 4.4BSD.

The
err_set_exit() and err_set_file() functions first appeared

in
FreeBSD 2.1. The errc() and warnc() functions first ap

peared in
FreeBSD 3.0.

BSD March 6, 1999

BSD