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Syslog(3pm)      User Contributed Perl Documentation     Syslog(3pm)

       Sys::Syslog - Perl interface to the UNIX syslog(3) calls

       Version 0.26

           use Sys::Syslog;
                   # all except setlogsock(), or:

           use Sys::Syslog qw(:DEFAULT setlogsock);
                   # default set, plus setlogsock()

           use Sys::Syslog qw(:standard :macros);
                   # standard functions, plus macros

           openlog $ident, $logopt, $facility;       # don't forget this
           syslog $priority, $format, @args;
           $oldmask = setlogmask $mask_priority;

       "Sys::Syslog" is an interface to the UNIX syslog(3) program.
       Call "syslog()" with a string priority and a list of
       "printf()" args just like syslog(3).

       You can find a kind of FAQ in "THE RULES OF SYS::SYSLOG".
       Please read it before coding, and again before asking

       "Sys::Syslog" exports the following "Exporter" tags:

       ·   ":standard" exports the standard syslog(3) functions:

               openlog closelog setlogmask syslog

       ·   ":extended" exports the Perl specific functions for


       ·   ":macros" exports the symbols corresponding to most of
           your syslog(3) macros and the "LOG_UPTO()" and
           "LOG_MASK()" functions.  See "CONSTANTS" for the
           supported constants and their meaning.

       By default, "Sys::Syslog" exports the symbols from the
       ":standard" tag.

       openlog($ident, $logopt, $facility)
           Opens the syslog.  $ident is prepended to every message.
           $logopt contains zero or more of the options detailed
           below.  $facility specifies the part of the system to
           report about, for example "LOG_USER" or "LOG_LOCAL0": see
           "Facilities" for a list of well-known facilities, and
           your syslog(3) documentation for the facilities available
           in your system.  Check "SEE ALSO" for useful links.
           Facility can be given as a string or a numeric macro.

           This function will croak if it can't connect to the
           syslog daemon.

           Note that "openlog()" now takes three arguments, just
           like openlog(3).

           You should use "openlog()" before calling "syslog()".


           ·   "cons" - This option is ignored, since the failover
               mechanism will drop down to the console automatically
               if all other media fail.

           ·   "ndelay" - Open the connection immediately (normally,
               the connection is opened when the first message is

           ·   "nofatal" - When set to true, "openlog()" and
               "syslog()" will only emit warnings instead of dying
               if the connection to the syslog can't be established.

           ·   "nowait" - Don't wait for child processes that may
               have been created while logging the message.  (The
               GNU C library does not create a child process, so
               this option has no effect on Linux.)

           ·   "perror" - Write the message to standard error output
               as well to the system log.

           ·   "pid" - Include PID with each message.


           Open the syslog with options "ndelay" and "pid", and with
           facility "LOCAL0":

               openlog($name, "ndelay,pid", "local0");

           Same thing, but this time using the macro corresponding
           to "LOCAL0":

               openlog($name, "ndelay,pid", LOG_LOCAL0);

       syslog($priority, $message)
       syslog($priority, $format, @args)
           If $priority permits, logs $message or "sprintf($format,
           @args)" with the addition that %m in $message or $format
           is replaced with "$!" (the latest error message).

           $priority can specify a level, or a level and a facility.
           Levels and facilities can be given as strings or as
           macros.  When using the "eventlog" mechanism, priorities
           "DEBUG" and "INFO" are mapped to event type
           "informational", "NOTICE" and "WARNIN" to "warning" and
           "ERR" to "EMERG" to "error".

           If you didn't use "openlog()" before using "syslog()",
           "syslog()" will try to guess the $ident by extracting the
           shortest prefix of $format that ends in a ":".


               # informational level
               syslog("info", $message);
               syslog(LOG_INFO, $message);

               # information level, Local0 facility
               syslog("info|local0", $message);
               syslog(LOG_INFO|LOG_LOCAL0, $message);

               "Sys::Syslog" version v0.07 and older passed the
               $message as the formatting string to "sprintf()" even
               when no formatting arguments were provided.  If the
               code calling "syslog()" might execute with older
               versions of this module, make sure to call the
               function as "syslog($priority, "%s", $message)"
               instead of "syslog($priority, $message)".  This
               protects against hostile formatting sequences that
               might show up if $message contains tainted data.

           Sets the log mask for the current process to
           $mask_priority and returns the old mask.  If the mask
           argument is 0, the current log mask is not modified.  See
           "Levels" for the list of available levels.  You can use
           the "LOG_UPTO()" function to allow all levels up to a
           given priority (but it only accept the numeric macros as


           Only log errors:

               setlogmask( LOG_MASK(LOG_ERR) );

           Log everything except informational messages:

               setlogmask( ~(LOG_MASK(LOG_INFO)) );

           Log critical messages, errors and warnings:

               setlogmask( LOG_MASK(LOG_CRIT)
                         | LOG_MASK(LOG_ERR)
                         | LOG_MASK(LOG_WARNING) );

           Log all messages up to debug:

               setlogmask( LOG_UPTO(LOG_DEBUG) );

       setlogsock($sock_type, $stream_location) (added in Perl
       setlogsock($sock_type, $stream_location, $sock_timeout)
       (added in 0.25)
           Sets the socket type to be used for the next call to
           "openlog()" or "syslog()" and returns true on success,
           "undef" on failure. The available mechanisms are:

           ·   "native" - use the native C functions from your
               syslog(3) library (added in "Sys::Syslog" 0.15).

           ·   "eventlog" - send messages to the Win32 events logger
               (Win32 only; added in "Sys::Syslog" 0.19).

           ·   "tcp" - connect to a TCP socket, on the "syslog/tcp"
               or "syslogng/tcp" service. If defined, the second
               parameter is used as a hostname to connect to.

           ·   "udp" - connect to a UDP socket, on the "syslog/udp"
               service.  If defined, the second parameter is used as
               a hostname to connect to, and the third parameter as
               the timeout used to check for UDP response.

           ·   "inet" - connect to an INET socket, either TCP or
               UDP, tried in that order.  If defined, the second
               parameter is used as a hostname to connect to.

           ·   "unix" - connect to a UNIX domain socket (in some
               systems a character special device).  The name of
               that socket is the second parameter or, if you omit
               the second parameter, the value returned by the
               "_PATH_LOG" macro (if your system defines it), or
               /dev/log or /dev/conslog, whatever is writable.

           ·   "stream" - connect to the stream indicated by the
               pathname provided as the optional second parameter,
               or, if omitted, to /dev/conslog.  For example Solaris
               and IRIX system may prefer "stream" instead of

           ·   "pipe" - connect to the named pipe indicated by the
               pathname provided as the optional second parameter,
               or, if omitted, to the value returned by the
               "_PATH_LOG" macro (if your system defines it), or
               /dev/log (added in "Sys::Syslog" 0.21).

           ·   "console" - send messages directly to the console, as
               for the "cons" option of "openlog()".

           A reference to an array can also be passed as the first
           parameter.  When this calling method is used, the array
           should contain a list of mechanisms which are attempted
           in order.

           The default is to try "native", "tcp", "udp", "unix",
           "pipe", "stream", "console".  Under systems with the
           Win32 API, "eventlog" will be added as the first
           mechanism to try if "Win32::EventLog" is available.

           Giving an invalid value for $sock_type will "croak".


           Select the UDP socket mechanism:


           Select the native, UDP socket then UNIX domain socket

               setlogsock(["native", "udp", "unix"]);

               Now that the "native" mechanism is supported by
               "Sys::Syslog" and selected by default, the use of the
               "setlogsock()" function is discouraged because other
               mechanisms are less portable across operating
               systems.  Authors of modules and programs that use
               this function, especially its cargo-cult form
               "setlogsock("unix")", are advised to remove any
               occurence of it unless they specifically want to use
               a given mechanism (like TCP or UDP to connect to a
               remote host).

           Closes the log file and returns true on success.

       The First Rule of Sys::Syslog is: You do not call

       The Second Rule of Sys::Syslog is: You do not call

       The Third Rule of Sys::Syslog is: The program crashes,
       "die"s, calls "closelog", the log is over.

       The Fourth Rule of Sys::Syslog is: One facility, one

       The Fifth Rule of Sys::Syslog is: One log at a time.

       The Sixth Rule of Sys::Syslog is: No "syslog" before

       The Seventh Rule of Sys::Syslog is: Logs will go on as long
       as they have to.

       The Eighth, and Final Rule of Sys::Syslog is: If this is your
       first use of Sys::Syslog, you must read the doc.

       An example:

           openlog($program, 'cons,pid', 'user');
           syslog('info', '%s', 'this is another test');
           syslog('mail|warning', 'this is a better test: %d', time);

           syslog('debug', 'this is the last test');

       Another example:

           openlog("$program $$", 'ndelay', 'user');
           syslog('notice', 'fooprogram: this is really done');

       Example of use of %m:

           $! = 55;
           syslog('info', 'problem was %m');   # %m == $! in syslog(3)

       Log to UDP port on $remotehost instead of logging locally:

           setlogsock("udp", $remotehost);
           openlog($program, 'ndelay', 'user');
           syslog('info', 'something happened over here');


       ·   "LOG_AUDIT" - audit daemon (IRIX); falls back to

       ·   "LOG_AUTH" - security/authorization messages

       ·   "LOG_AUTHPRIV" - security/authorization messages

       ·   "LOG_CONSOLE" - "/dev/console" output (FreeBSD); falls
           back to "LOG_USER"

       ·   "LOG_CRON" - clock daemons (cron and at)

       ·   "LOG_DAEMON" - system daemons without separate facility

       ·   "LOG_FTP" - FTP daemon

       ·   "LOG_KERN" - kernel messages

       ·   "LOG_INSTALL" - installer subsystem (Mac OS X); falls
           back to "LOG_USER"

       ·   "LOG_LAUNCHD" - launchd - general bootstrap daemon (Mac
           OS X); falls back to "LOG_DAEMON"

       ·   "LOG_LFMT" - logalert facility; falls back to "LOG_USER"

       ·   "LOG_LOCAL0" through "LOG_LOCAL7" - reserved for local

       ·   "LOG_LPR" - line printer subsystem

       ·   "LOG_MAIL" - mail subsystem

       ·   "LOG_NETINFO" - NetInfo subsystem (Mac OS X); falls back
           to "LOG_DAEMON"

       ·   "LOG_NEWS" - USENET news subsystem

       ·   "LOG_NTP" - NTP subsystem (FreeBSD, NetBSD); falls back
           to "LOG_DAEMON"

       ·   "LOG_RAS" - Remote Access Service (VPN / PPP) (Mac OS X);
           falls back to "LOG_AUTH"

       ·   "LOG_REMOTEAUTH" - remote authentication/authorization
           (Mac OS X); falls back to "LOG_AUTH"

       ·   "LOG_SECURITY" - security subsystems (firewalling, etc.)
           (FreeBSD); falls back to "LOG_AUTH"

       ·   "LOG_SYSLOG" - messages generated internally by syslogd

       ·   "LOG_USER" (default) - generic user-level messages

       ·   "LOG_UUCP" - UUCP subsystem


       ·   "LOG_EMERG" - system is unusable

       ·   "LOG_ALERT" - action must be taken immediately

       ·   "LOG_CRIT" - critical conditions

       ·   "LOG_ERR" - error conditions

       ·   "LOG_WARNING" - warning conditions

       ·   "LOG_NOTICE" - normal, but significant, condition

       ·   "LOG_INFO" - informational message

       ·   "LOG_DEBUG" - debug-level message

       "Invalid argument passed to setlogsock"
           (F) You gave "setlogsock()" an invalid value for

       "eventlog passed to setlogsock, but no Win32 API available"
           (W) You asked "setlogsock()" to use the Win32 event
           logger but the operating system running the program isn't
           Win32 or does not provides Win32 compatible facilities.

       "no connection to syslog available"
           (F) "syslog()" failed to connect to the specified socket.

       "stream passed to setlogsock, but %s is not writable"
           (W) You asked "setlogsock()" to use a stream socket, but
           the given path is not writable.

       "stream passed to setlogsock, but could not find any device"
           (W) You asked "setlogsock()" to use a stream socket, but
           didn't provide a path, and "Sys::Syslog" was unable to
           find an appropriate one.

       "tcp passed to setlogsock, but tcp service unavailable"
           (W) You asked "setlogsock()" to use a TCP socket, but the
           service is not available on the system.

       "syslog: expecting argument %s"
           (F) You forgot to give "syslog()" the indicated argument.

       "syslog: invalid level/facility: %s"
           (F) You specified an invalid level or facility.

       "syslog: too many levels given: %s"
           (F) You specified too many levels.

       "syslog: too many facilities given: %s"
           (F) You specified too many facilities.

       "syslog: level must be given"
           (F) You forgot to specify a level.

       "udp passed to setlogsock, but udp service unavailable"
           (W) You asked "setlogsock()" to use a UDP socket, but the
           service is not available on the system.

       "unix passed to setlogsock, but path not available"
           (W) You asked "setlogsock()" to use a UNIX socket, but
           "Sys::Syslog" was unable to find an appropriate an
           appropriate device.

       Manual Pages


       SUSv3 issue 6, IEEE Std 1003.1, 2004 edition,

       GNU C Library documentation on syslog,

       Solaris 10 documentation on syslog,

       Mac OS X documentation on syslog,

       IRIX 6.5 documentation on syslog,

       AIX 5L 5.3 documentation on syslog,

       HP-UX 11i documentation on syslog,

       Tru64 5.1 documentation on syslog,

       Stratus VOS 15.1,


       RFC 3164 - The BSD syslog Protocol,
       <> -- Please note that
       this is an informational RFC, and therefore does not specify
       a standard of any kind.

       RFC 3195 - Reliable Delivery for syslog,


       Syslogging with Perl,

       Event Log

       Windows Event Log,

       Tom Christiansen <tchrist (at)> and Larry Wall
       <larry (at)>.

       UNIX domain sockets added by Sean Robinson <robinson_s (at)> with support from Tim Bunce <Tim.Bunce (at)> and the "perl5-porters" mailing list.

       Dependency on replaced with XS code by Tom Hughes
       <tom (at)>.

       Code for "constant()"s regenerated by Nicholas Clark <nick

       Failover to different communication modes by Nick Williams
       <Nick.Williams (at)>.

       Extracted from core distribution for publishing on the CPAN
       by Sebastien Aperghis-Tramoni <sebastien (at)>.

       XS code for using native C functions borrowed from
       "Unix::Syslog", written by Marcus Harnisch <marcus.harnisch

       Yves Orton suggested and helped for making "Sys::Syslog" use
       the native event logger under Win32 systems.

       Jerry D. Hedden and Reini Urban provided greatly appreciated
       help to debug and polish "Sys::Syslog" under Cygwin.

       Please report any bugs or feature requests to "bug-sys-syslog
       (at)", or through the web interface at
       I will be notified, and then you'll automatically be notified
       of progress on your bug as I make changes.

       You can find documentation for this module with the perldoc

           perldoc Sys::Syslog

       You can also look for information at:

       ·   AnnoCPAN: Annotated CPAN documentation


       ·   CPAN Ratings


       ·   RT: CPAN's request tracker


       ·   Search CPAN


       ·   Kobes' CPAN Search


       ·   Perl Documentation


       Copyright (C) 1990-2008 by Larry Wall and others.

       This program is free software; you can redistribute it and/or
       modify it under the same terms as Perl itself.

perl v5.10.0                 2008-06-17                  Syslog(3pm)
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