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

NAME

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

SYNOPSIS

	use Unix::Syslog qw(:macros);  # Syslog macros
	use Unix::Syslog qw(:subs);    # Syslog functions

	openlog $ident, $option, $facility;
	syslog $priority, $format, @formatargs;
	closelog;
	$oldmask = setlogmask $mask_priority;

DESCRIPTION

       This module provides an interface to the system logger syslogd(8) via Perl's XSUBs. The implementation attempts to resemble the native
       libc-functions of your system, so that anyone being familiar with syslog.h should be able to use this module right away.

       In contrary to Sys::Syslog(3), this modules does not open a network connection to send the messages. This can help you to avoid opening
       security holes in your computer (see "FAQ").

       The subs imported by the tag "macros" are simply wrappers around the most important "#defines" in your system's C header file syslog.h. The
       macros return integer values that are used to specify options, facilities and priorities in a more or less portable way. They also provide
       general information about your local syslog mechanism. Check syslog(3) and your local syslog.h for information about the macros, options
       and facilities available on your system.

       The following functions are provided:

       openlog $ident, $option, $facility
	   opens a connection to the system logger.  $ident is an identifier string that syslogd(8) prints into every message. It usually equals
	   the process name. $option is an integer value that is the result of ORed options. $facility is an integer value that specifies the part
	   of the system the message should be associated with (e.g. kernel message, mail subsystem).

       syslog $priority, $format, @formatargs
	   Generates a log message and passes it to the system logger. If "syslog()" is called without calling "openlog()" first, probably system
	   dependent default values will be used as arguments for an implicit call to "openlog()".

	   $priority is an integer value that specifies the priority of the message. Alternatively $priority can be the ORed value of a priority
	   and a facility. In that case a previously selected facility will be overridden.

	   In the case that "syslog()" is called without calling "openlog()" first and priority does not specify both a priority and a facility, a
	   default facility will be used. This behaviour is most likely system dependent and the user should not rely on any particular value in
	   that case.

	   $format is a format string in the style of printf(3). Additionally to the usual printf directives %m can be specified in the string. It
	   will be replaced implicitly by the contents of the Perl variable $! ($ERRNO). @formatargs is a list of values that the format
	   directives will be replaced with subsequently.

       closelog
	   closes the connection to the system logger.

       setlogmask $mask_priority
	   sets the priority mask and returns the old mask. Logging is enabled for the priorities indicated by the bits in the mask that are set
	   and is disabled where the bits are not set. Macros are provided to specify valid and portable arguments to "setlogmask()". Usually the
	   default log mask allows all messages to be logged.

       priorityname $priority
	   returns a string containing the name of $priority as string. If this functionality has not been enabled at installation, the function
	   returns undef.

       facilityname $facility
	   returns a string containing the name of $facility as string. If this functionality has not been enabled at installation, the function
	   returns undef.

       NOTE: The behaviour of this module is system dependent. It is highly recommended to consult your system manual for available macros and the
       behaviour of the provided functions.

RETURN VALUES

       The functions openlog(), syslog() and closelog() return the undefined value. The function setlogmask returns the previous mask value.

EXAMPLES

       Open a channel to syslogd specifying an identifier (usually the process name) some options and the facility:
	 "openlog "test.pl", LOG_PID | LOG_PERROR, LOG_LOCAL7;"

       Generate log message of specified priority using a printf-type formatted string:
	 "syslog LOG_INFO, "This is message number %d", 42;"

       Set log priority mask to block all messages but those of priority "LOG_DEBUG":
	 "$oldmask = setlogmask(LOG_MASK(LOG_DEBUG))"

       Set log priority mask to block all messages with a higher priority than "LOG_ERR":
	 "$oldmask = setlogmask(LOG_UPTO(LOG_ERR))"

       Close channel to syslogd:
	 "closelog;"

FAQ

       1.  What is the benefit of using this module instead of Sys::Syslog?

	   Sys::Syslog always opens a network connection to the syslog service. At least on Linux systems this may lead to some trouble, because

	   o   Linux syslogd (from package sysklogd) does not listen to the network by default. Most people working on stand-alone machines
	       (including me) didn't see any reason why to enable this option. Others didn't enable it for security reasons.

	       OS-independent, some sysadmins may run a firewall on their network that blocks connections to port 514/udp.

	   o   By default Linux syslogd doesn't forward messages which have already already received from the network to other log hosts. There
	       are reasons not to enable this option unless it is really necessary. Looping messages resulting from a misconfiguration may break
	       down your (log-)system.

	   Peter Stamfest <peter.stamfest@eunet.at> pointed out some other advantages of Unix::Syslog, I didn't came across my self.

	   o   LOG_PERROR works.

	   o   works with perl -Tw without warnings and problems due to tainted data as it is the case for Sys::Syslog in some special
	       applications. [Especially when running a script as root]

       2.  Well, is there any reason to use Sys::Syslog any longer?

	   Yes! In contrary to Unix::Syslog, Sys::Syslog works even if you don't have a syslog daemon running on your system as long as you are
	   connected to a log host via a network and have access to the syslog.h header file of your log host to generate the initial files for
	   Sys::Syslog (see Sys::Syslog(3) for details). Unix::Syslog only logs to your local syslog daemon which in turn may be configured to
	   distribute the message over the network.

       3.  Are calls to the functions provided by Unix::Syslog compatible to those of Sys::Syslog?

	   Currently not. Sys::Syslog requires strings to specify many of the arguments to the functions, while Unix::Syslog uses numeric
	   constants accessed via macros as defined in syslog.h. Although the strings used by Sys::Syslog are also defined in syslog.h, it seems
	   that most people got used to the numeric arguments. I will implement the string based calls if there are enough people ($min_people >
	   10**40) complaining about the lack of compatibility.

SEE ALSO

       syslog(3), Sys::Syslog(3), syslogd(8), perl(1)

AUTHOR

       Marcus Harnisch <marcus.harnisch@gmx.net>

perl v5.16.2							    2008-05-18								 Syslog(3)