NAME
err, verr,
errc, verrc,
errx, verrx,
warn, vwarn,
warnc, vwarnc,
warnx, vwarnx,
err_set_exit, err_set_file
— formatted error
messages
LIBRARY
library “libc”
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
Theerr()
and
warn()
family of functions display a formatted error message on the standard error
output, or on another file specified 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 supplied error code value 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(),
verrx(),
warnx(),
and
vwarnx()
functions do not append an error message.
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(EX_OSERR, NULL); if ((fd = open(file_name, O_RDONLY, 0)) == -1) err(EX_NOINPUT, "%s", file_name);
Display an error message and exit:
if (tm.tm_hour < START_TIME) errx(EX_DATAERR, "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(EX_OSFILE, "%s", block_device);
Warn of an error without using the global variable errno:
error = my_function(); /* returns a value from <errno.h> */ if (error != 0) warnc(error, "my_function");
SEE ALSO
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 appeared in
FreeBSD 3.0.