ERR(3)

NAME
err, verr, errx, verrx, warn, vwarn, warnx, vwarnx, - formatted error messages

SYNOPSIS
#include <err.h>
void
err(int eval, const char *fmt, ...);
void
errx(int eval, const char *fmt, ...);
void
warn(const char *fmt, ...);
void
warnx(const char *fmt, ...);
#include <stdarg.h>
void
verr(int eval, 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
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. 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(), verr(), warn(), and vwarn() 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.

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 message.

The err(), verr(), errx(), and verrx() functions do not return, but exit with the value of the argument eval.

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);

CONFORMING TO
These functions are non-standard BSD extensions.

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

SEE ALSO
error(3), exit(3), printf(3), perror(3), strerror(3)