ERR(3)

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

SYNOPSIS
void
err(eval, fmt, ...)
    int eval;
    char *fmt;

void
verr(eval, fmt, args)
    int eval;
    char *fmt;
    va_list args;

void
errx(eval, fmt, ...)
    int eval;
    char *fmt;

void
verrx(eval, fmt, args)
    int eval
    char *fmt;
    va_list args;

void
warn(fmt, ...)
    char *fmt;

void
vwarn(fmt, args)
    char *fmt;
    va_list args;

void
warnx(fmt, ...)
    char *fmt;

void
vwarnx(fmt, args)
    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, a colon character, and a space are 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. 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)
	err(1, "%s", block_device);

SEE ALSO
strerror(3)

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