redhat man page for errx

ERR(3)							   BSD Library Functions Manual 						    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);

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

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

BSD
								   March 6, 1999							       BSD