bsd man page for err

ERR(3)							     Library Functions Manual							    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 charac-
       ter, 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.

4th Berkeley Distribution					 February 3, 1995							    ERR(3)