iOS Manual Pages

This document is a Mac OS X manual page. Manual pages are a command-line technology for providing documentation. You can view these manual pages locally using the man(1) command. These manual pages come from many different sources, and thus, have a variety of writing styles.

For more information about the manual page format, see the manual page for manpages(5).

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 mes-sage message
     sage 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 code 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 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.  The
     err_set_file() function sets the output stream used by the other func-tions. functions.
     tions.  Its vfp argument must be either a pointer to an open stream (pos-sibly (possibly
     sibly 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(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);

     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