syslog(3C)

NAME
     syslog, openlog, closelog, setlogmask, vsyslog - control system log

SYNOPSIS
     #include <syslog.h>

     void openlog(const char *ident, int logopt, int facility);

     void syslog(int priority, const char *message, parameters...);

     void closelog(void);

     int setlogmask(int maskpri);

     void vsyslog(int priority, const char *message, va_list ap);

DESCRIPTION
     Syslog arranges to write message onto the system log maintained by
     syslogd(1M).  The message is tagged with priority.  The message looks
     like a printf(3S) string except that %m is replaced by the current error
     message (collected from errno).  A trailing newline is added if needed.
     This message will be read by syslogd(1M) and written to the system
     console, log files, or forwarded to syslogd on another host as
     appropriate.  Vsyslog is like syslog except that instead of being called
     with a variable number of arguments, it is called with an argument list
     as defined by stdarg(5).

     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 an ordered 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, e.g., 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.
     If syslog cannot pass the message to syslogd, it will attempt to write
     the message on /dev/console if the LOG_CONS option is set (see below).

     If special processing is needed, openlog can be called to initialize the
     log file.  The parameter ident is a string that is prepended to every
     message.  Logopt is a bit field indicating logging options.

     Current values for logopt are:

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

     LOG_CONS      Force writing messages to the console if unable to send it
                   to syslogd. This option is safe to use in daemon processes
                   that have no controlling terminal since syslog will fork
                   before opening the console.

     LOG_ODELAY    Delay opening the connection to syslogd until the first
                   syslog call. This is the default.

     LOG_NDELAY    Open the connection to syslogd immediately.  Useful for
                   programs that need to manage the order in which file
                   descriptors are allocated.

     LOG_NOWAIT    Don't wait for children forked to log messages on the
                   console.  This option should be used by processes that
                   enable notification of child termination via SIGCHLD, as
                   syslog may otherwise block waiting for a child whose exit
                   status has already been collected.

     LOG_PERROR    Write messages to stderr as well as to syslogd.

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

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

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

     LOG_MAIL      The mail system.

     LOG_DAEMON    System daemons, such as routed(1M), ftpd(1M), rshd(1M),
                   etc.

     LOG_AUTH      The authorization system:  login(1), su(1M), getty(1M),
                   etc.  ftpd(1M), and rshd(1M) also use LOG_AUTH.

     LOG_LPR       The line printer spooling system:  lpr(1), lpd(1M), etc.
     LOG_NEWS      The network news system.

     LOG_UUCP      The UNIX-to-UNIX Copy system:  uucp(1C), uucico(1M),
                   uux(1C), etc.

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

     Closelog can be used to close the log file.

     Setlogmask sets the log priority mask to maskpri and returns the previous
     mask.  Calls to syslog 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.


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
     syslogd(1M)