err(3)                                                           err(3)

  err()

  NAME

    err(), verr(), errx(), verrx(), warn(), vwarn(), warnx(), vwarnx() -
    formatted error messages

  SYNOPSIS

    #include 

    void err (int eval, const char *fmt, ...)
    void verr (int eval, const char *fmt, va_list args)
    void errx (int eval, const char *fmt, ...)
    void verrx (int eval, const char *fmt, va_list args)
    void warn (const char *fmt, ...)
    void vwarn (const char *fmt, va_list args)
    void warnx (const char *fmt, ...)
    void vwarnx (const char *fmt, va_list args)

  DESCRIPTION

    The err(3) and warn(3) 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 first. If the
    fmt argument is not NULL, the formatted error message, a colon character,
    and a space are output. In the case of the err(3), verr(3), warn(3), and
    vwarn(3) 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.

  RETURN VALUES

    The err(3), verr(3), errx(3), and verrx(3) 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)

  USAGE NOTES

    All of these functions are thread safe.

    None of these functions are async-signal safe.