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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_exit_b, 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_exit_b(void (^exitb)(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 out-put, output,
     put, 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 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_exit_b() function is like err_set_exit() except it takes a block
     pointer instead of a function pointer.

           Note: The Block_copy() function (defined in <Blocks.h>) is used by err_set_exit_b() to make a
           copy of the block, especially for the case when a stack-based block might go out of scope when
           the subroutine returns.

     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() func-tions functions
     tions first appeared in FreeBSD 2.1.  The errc() and warnc() functions first appeared in FreeBSD 3.0.
     The err_set_exit_b() function first appeared in Mac OS X 10.6.

BSD                              May 20, 2008                              BSD