perldoc > Sys::Syslog

📛 NAME

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

🚀 Quick Reference

Use CaseCommandDescription
📝 Basic Loggingopenlog($ident, $logopt, $facility); syslog($priority, $format, @args); closelog();Standard syslog workflow: open, send, close.
🛡️ Set Log Masksetlogmask(LOG_MASK(LOG_ERR));Filter messages to only log errors.
🌐 UDP Socketsetlogsock("udp");Send logs via UDP to local syslog daemon.
🖥️ Remote Syslog (TCP)setlogsock({ type => "tcp", host => $host });Send logs to a remote host over TCP.
⚙️ Custom Optionsopenlog($name, "ndelay,pid", "local0");Open syslog with immediate connection and PID.
📋 Log with Facility & Prioritysyslog('mail|warning', 'message');Log a warning under the mail facility.

📦 VERSION

This is the documentation of version 0.36

📋 SYNOPSIS

use Sys::Syslog;                        # all except setlogsock()
use Sys::Syslog qw(:standard :macros);  # standard functions & macros

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

📖 DESCRIPTION

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).

📤 EXPORTS

Sys::Syslog exports the following Exporter tags:

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

⚙️ FUNCTIONS

⚙️ 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().

🔧 Options

💡 Examples

openlog($name, "ndelay,pid", "local0");
openlog($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 WARNING 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 :.

💡 Examples

syslog("info", $message);
syslog(LOG_INFO, $message);
syslog("info|local0", $message);
syslog(LOG_INFO|LOG_LOCAL0, $message);

⚠️ Note

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.

⚙️ setlogmask($mask_priority)

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 arguments).

💡 Examples

setlogmask( LOG_MASK(LOG_ERR) );
setlogmask( ~(LOG_MASK(LOG_INFO)) );
setlogmask( LOG_MASK(LOG_CRIT)
          | LOG_MASK(LOG_ERR)
          | LOG_MASK(LOG_WARNING) );
setlogmask( LOG_UPTO(LOG_DEBUG) );

⚙️ setlogsock()

Sets the socket type and options to be used for the next call to openlog() or syslog(). Returns true on success, undef on failure.

Being Perl-specific, this function has evolved along time. It can currently be called as follow:

📋 Options

📋 Mechanisms

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.

💡 Examples

setlogsock("udp");
setlogsock({ type => "tcp", port => 2486 });
setlogsock({ type => "tcp", host => $loghost });
setlogsock(["native", "udp", "unix"]);

⚠️ Note

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 occurrence of it unless they specifically want to use a given mechanism (like TCP or UDP to connect to a remote host).

⚙️ closelog()

Closes the log file and returns true on success.

📜 THE RULES OF SYS::SYSLOG

  1. The First Rule of Sys::Syslog is: You do not call setlogsock.
  2. The Second Rule of Sys::Syslog is: You do not call setlogsock.
  3. The Third Rule of Sys::Syslog is: The program crashes, dies, calls closelog, the log is over.
  4. The Fourth Rule of Sys::Syslog is: One facility, one priority.
  5. The Fifth Rule of Sys::Syslog is: One log at a time.
  6. The Sixth Rule of Sys::Syslog is: No syslog before openlog.
  7. The Seventh Rule of Sys::Syslog is: Logs will go on as long as they have to.
  8. The Eighth, and Final Rule of Sys::Syslog is: If this is your first use of Sys::Syslog, you must read the doc.

🧪 EXAMPLES

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

syslog('debug', 'this is the last test');
openlog("$program $$", 'ndelay', 'user');
syslog('notice', 'fooprogram: this is really done');
$! = 55;
syslog('info', 'problem was %m');   # %m == $! in syslog(3)
setlogsock("udp", $remotehost);
openlog($program, 'ndelay', 'user');
syslog('info', 'something happened over here');

🏷️ CONSTANTS

🏷️ Facilities

🏷️ Levels

🩺 DIAGNOSTICS

📜 HISTORY

Sys::Syslog is a core module, part of the standard Perl distribution since 1990. At this time, modules as we know them didn't exist, the Perl library was a collection of .pl files, and the one for sending syslog messages with was simply lib/syslog.pl, included with Perl 3.0. It was converted as a module with Perl 5.0, but had a version number only starting with Perl 5.6. Here is a small table with the matching Perl and Sys::Syslog versions.

Sys::SyslogPerl
undef5.0.0 ~ 5.5.4
0.015.6.*
0.035.8.0
0.045.8.1, 5.8.2, 5.8.3
0.055.8.4, 5.8.5, 5.8.6
0.065.8.7
0.135.8.8
0.225.10.0
0.275.8.9, 5.10.1 ~ 5.14.*
0.295.16.*
0.325.18.*
0.335.20.*
0.335.22.*

🔗 SEE ALSO

📚 Other modules

📄 Manual Pages

📄 RFCs

📰 Articles

📋 Event Log

👤 AUTHORS & ACKNOWLEDGEMENTS

Tom Christiansen <tchrist (at) perl.com> and Larry Wall <larry (at) wall.org>.

UNIX domain sockets added by Sean Robinson <robinson_s (at) sc.maricopa.edu> with support from Tim Bunce <Tim.Bunce (at) ig.co.uk> and the perl5-porters mailing list.

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

Code for constant()s regenerated by Nicholas Clark <nick (at) ccl4.org>.

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

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

XS code for using native C functions borrowed from Unix::Syslog, written by Marcus Harnisch <marcus.harnisch (at) gmx.net>.

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.

🐛 BUGS

Please report any bugs or feature requests to bug-sys-syslog (at) rt.cpan.org, or through the web interface at http://rt.cpan.org/Public/Dist/Display.html?Name=Sys-Syslog. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

🆘 SUPPORT

You can find documentation for this module with the perldoc command.

perldoc Sys::Syslog

You can also look for information at:

The source code is available on Git Hub: https://github.com/maddingue/Sys-Syslog/

©️ COPYRIGHT

Copyright (C) 1990-2012 by Larry Wall and others.

📄 LICENSE

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

Sys::Syslog □✕
📛 NAME 🚀 Quick Reference 📦 VERSION 📋 SYNOPSIS 📖 DESCRIPTION 📤 EXPORTS ⚙️ FUNCTIONS
⚙️ openlog($ident, $logopt, $facility) ⚙️ syslog($priority, $message) ⚙️ syslog($priority, $format, @args) ⚙️ setlogmask($mask_priority) ⚙️ setlogsock() ⚙️ closelog()
📜 THE RULES OF SYS::SYSLOG 🧪 EXAMPLES 🏷️ CONSTANTS
🏷️ Facilities 🏷️ Levels
🩺 DIAGNOSTICS 📜 HISTORY 🔗 SEE ALSO
📚 Other modules 📄 Manual Pages 📄 RFCs 📰 Articles 📋 Event Log
👤 AUTHORS & ACKNOWLEDGEMENTS 🐛 BUGS 🆘 SUPPORT ©️ COPYRIGHT 📄 LICENSE

Generated by phpman v4.9.26-5-g7740029 · Markdown · JSON · MCP Author: Che Dong Under GNU General Public License
2026-08-12 12:59 @216.73.217.60
CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
Valid XHTML 1.0 Transitional!Valid CSS!

^_top_^