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

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 v5.10.0                      2008-05-18                       Syslog(3pm)

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