vsyslog(3)                                                   vsyslog(3)

  syslog()

  NAME

    syslog(), vsyslog(), openlog(), closelog(), setlogmask() - control system
    log

  SYNOPSIS

    #include 
    #include 

    void syslog (int priority, const char *message, ...)
    void vsyslog (int priority, const char *message, va_list args)
    void openlog (const char *ident, int logopt, int facility)
    void closelog (void)
    int setlogmask (int maskpri)

  DESCRIPTION

    The syslog(3) function writes message to the system message logger. The
    message is then written to log files, logged-in users, or forwarded to
    other machines as appropriate. (See syslogd(1).) If the syslogd(1) program
    is not running, the message is written to the file /var/adm/log/logger.

    The message is identical to a printf(3) format string, except that %m is
    replaced by the current error message (as denoted by the global variable
    errno; see strerror(3)). A trailing newline is added if none is present.

    The vsyslog(3) function is an alternate form in which the arguments have
    already been captured using the variable-length argument facilities of
    stdarg(3) (note that it is not varargs, as in many implementations).

    The message is tagged with priority. Priorities are encoded as a facility
    and a level. The facility describes the part of the system generating the
    message. The level is selected from the following ordered (high to low)
    list:

    LOG_EMERG
        A panic condition. This is normally broadcast to all users.

    LOG_ALERT
        A condition that should be corrected immediately, such as a corrupted
        system database.

    LOG_CRIT
        Critical conditions such as hard device errors.

    LOG_ERR
        Errors.

    LOG_WARNING
        Warning messages.

    LOG_NOTICE
        Conditions that are not error conditions, but should possibly be
        handled specially.

    LOG_INFO
        Informational messages.

    LOG_DEBUG
        Messages that contain information normally of use only when debugging
        a program.

    The openlog(3) function provides for more specialized processing of the
    messages sent by syslog(3) and vsyslog(3). The parameter ident is a string
    that will be prepended to every message. The logopt argument is a bit
    field specifying logging options, which is formed by ORing one or more of
    the following values:

    LOG_NDELAY
        Open the connection to syslogd(1) immediately. Normally the open is
        delayed until the first message is logged. Useful for programs that
        need to manage the order in which file descriptors are allocated.

    LOG_PERROR
        Write the message to standard error output as well to the system log.

    LOG_PID
        Log the process id with each message: useful for identifying
        instantiations of daemons.

    The facility parameter encodes a default facility to be assigned to all
    messages that do not have an explicit facility encoded:

    LOG_AUTH
        The authorization system: login(1).

    LOG_AUTHPRIV
        The same as LOG_AUTH, but logged to a file readable only by selected
        individuals.

    LOG_CRON
        The clock daemon.

    LOG_DAEMON
        System daemons, such as routed(1), that are not provided for
        explicitly by other facilities.

    LOG_KERN
        Messages generated by the INTERIX subsystem. These cannot be generated
        by any user processes.

    LOG_FTP
        The file transfer protocol (FTP) daemon.

    LOG_LPR
        The line printer spooling system: lp(1).

    LOG_MAIL
        The mail system.

    LOG_NEWS
        The network news system.

    LOG_SYSLOG
        Messages generated internally by syslogd(1).

    LOG_USER
        Messages generated by random user processes. This is the default
        facility identifier if none is specified.

    LOG_UUCP
        The uucp system.

    LOG_LOCAL0
        Reserved for local use. Similarly for LOG_LOCAL1 through LOG_LOCAL7.

    The closelog(3) function can be used to close the log file.

    The setlogmask(3) function sets the log priority mask to maskpri and
    returns the previous mask. Calls to syslog(3) with a priority not set in
    maskpri are rejected. The mask for an individual priority pri is
    calculated by the macro LOG_MASK(pri); the mask for all priorities up to
    and including toppri is given by the macro LOG_UPTO(toppri);. The default
    allows all priorities to be logged.

  RETURN VALUES

    The routines closelog(3), openlog(3), syslog(3), and vsyslog(3) return no
    value.

    The routine setlogmask(3) always returns the previous log mask level.

  EXAMPLES

    syslog(LOG_ALERT, "who: internal error 23");
    openlog("ftpd", LOG_PID, LOG_DAEMON);
    setlogmask(LOG_UPTO(LOG_ERR));
    syslog(LOG_INFO, "Connection from host %d", CallingHost);
    syslog(LOG_INFO|LOG_LOCAL2, "foobar error: %m");

  SEE ALSO

    logger(1)

    syslogd(1)

  USAGE NOTES

    All of these functions are thread safe.

    None of these functions are async-signal safe.