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ERR(3)				   BSD Library Functions Manual 			   ERR(3)

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <err.h>

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

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

     void
     err_set_file(void *vfp);

     void
     errc(int eval, int code, const char *fmt, ...);

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

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

     void
     warnc(int code, const char *fmt, ...);

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

     #include <stdarg.h>

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

     void
     verrc(int eval, int code, 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
     vwarnc(int code, 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, 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 printf(3)-like formatted error message is output.  The output
     is terminated by a newline character.

     The err(), errc(), verr(), verrc(), warn(), warnc(), vwarn(), and vwarnc() functions append
     an error message obtained from strerror(3) based on a supplied error code value or the
     global variable errno, preceded by another colon and space unless the fmt argument is NULL.

     In the case of the errc(), verrc(), warnc(), and vwarnc() functions, the code argument is
     used to look up the error message.

     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(), errc(), verrc(), errx(), and verrx() functions do not return, but exit
     with the value of the argument eval.  It is recommended that the standard values defined in
     sysexits(3) be used for the value of eval.  The err_set_exit() function can be used to spec-
     ify 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.  The err_set_file() function
     sets the output stream used by the other functions.  Its vfp argument must be either a
     pointer to an open stream (possibly already converted to void *) or a null pointer (in which
     case the output stream is set to standard error).

EXAMPLES
     Display the current errno information string and exit:

	   if ((p = malloc(size)) == NULL)
		   err(EX_OSERR, NULL);
	   if ((fd = open(file_name, O_RDONLY, 0)) == -1)
		   err(EX_NOINPUT, "%s", file_name);

     Display an error message and exit:

	   if (tm.tm_hour < START_TIME)
		   errx(EX_DATAERR, "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(EX_OSFILE, "%s", block_device);

     Warn of an error without using the global variable errno:

	   error = my_function();  /* returns a value from <errno.h> */
	   if (error != 0)
		   warnc(error, "my_function");

SEE ALSO
     exit(3), fmtmsg(3), printf(3), strerror(3), sysexits(3)

HISTORY
     The err() and warn() functions first appeared in 4.4BSD.  The err_set_exit() and
     err_set_file() functions first appeared in FreeBSD 2.1.  The errc() and warnc() functions
     first appeared in FreeBSD 3.0.

BSD					  March 6, 1999 				      BSD
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