ERR(3)

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

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);
void err_set_file (void *fp);
void err_set_exit (void (*exitf)(int));

DESCRIPTION
The err 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 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) 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.

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
exit(3), strerror(3)

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