ERR(3)

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

LIBRARY
libc

SYNOPSIS
#include <err.h>
void
err(int eval, const char *fmt, ...);
void
verr(int eval, const char *fmt, va_list args);
void
errx(int eval, const char *fmt, ...);
void
verrx(int eval, const char *fmt, va_list args);
void
warn(const char *fmt, ...);
void
vwarn(const char *fmt, va_list args);
void
warnx(const char *fmt, ...);
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 formatted error message is output. In the case of the err(), verr(), warn(), and vwarn() functions, the error message string affiliated with the current value of the global variable errno is output next, preceded by a colon character and a space if fmt is not NULL. In all cases, the output is followed by a newline character.

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)
    	warn("%s", block_device);

SEE ALSO
strerror(3)

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