posix man page for err

ERR(3)							     Linux Programmer's 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  mes-
       sage 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 the global variable errno, pre-
       ceded by another colon and space unless the fmt argument is NULL.

       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.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       +------------------+---------------+----------------+
       |Interface	  | Attribute	  | Value	   |
       +------------------+---------------+----------------+
       |err(), errx(),	  | Thread safety | MT-Safe locale |
       |warn(), warnx(),  |		  |		   |
       |verr(), verrx(),  |		  |		   |
       |vwarn(), vwarnx() |		  |		   |
       +------------------+---------------+----------------+

CONFORMING TO
       These functions are nonstandard BSD extensions.

EXAMPLE
       Display the current errno information string and exit:

	   p = malloc(size);
	   if (p == NULL)
	       err(1, NULL);
	   fd = open(file_name, O_RDONLY, 0);
	   if (fd == -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:

	   fd = open(raw_device, O_RDONLY, 0);
	   if (fd == -1)
	       warnx("%s: %s: trying the block device",
		       raw_device, strerror(errno));
	   fd = open(block_device, O_RDONLY, 0);
	   if (fd == -1)
	       err(1, "%s", block_device);

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

COLOPHON
       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux								    2017-09-15								    ERR(3)