NAME - Library for MRTG and support scripts


    use MRTG_lib;
    my ($configfile, @target_names, %globalcfg, %targetcfg);
    readcfg($configfile, \@target_names, \%globalcfg, \%targetcfg);
    my (@parsed_targets);
    cfgcheck(\@target_names, \%globalcfg, \%targetcfg, \@parsed_targets);


   MRTG_lib is part of MRTG, the Multi Router Traffic Grapher. It was
   separated from MRTG to allow other programs to easily use the same
   config files. The main part of MRTG_lib is the config file parser but
   some other funcions are there too.

       Type of OS: WIN, UNIX, VMS

       Slash in the current OS.

       Path separator in PATH variable

       "readcfg($file, \@targets, \%globalcfg, \%targetcfg [, $prefix,

       Reads a config file, parses it and fills some arrays and hashes.
       The mandatory arguments are: the name of the config file, a ref to
       an array which will be filled with a list of the target names, a
       hashref for the global configuration, a hashref for the target

       The configuration file syntax is:

        globaloption: value
        targetoption[targetname]: value
        aprefix*extglobal: value
        aprefix*exttarget[target2]: value


        workdir: /var/stat/mrtg
        14all*columns: 2

       The global config hash has the structure

        $globalcfg{configoption} = 'value'

       The target config hash has the structure

        $targetcfg{configoption}{targetname} = 'value'

       See mrtg-reference for more information about the MRTG
       configuration syntax.

       "readcfg" can take two additional arguments to extend the config
       file syntax. This allows programs to put their configuration into
       the mrtg config file. The fifth argument is the prefix of the
       extension, the sixth argument is a hash with the checkrules for
       these extension settings. E.g. if the prefix is "14all" "readcfg"
       will check config lines that begin with "14all*", i.e. all lines

        14all*columns: 2
        14all*graphsize[target3]: 500 200

       against the rules in %extrules. The format of this hash is:

        $extrules{option} = [sub{$_[0] =~ m/^\d+$/}, sub{"Error message for $_[0]"}]
        $extrules{option}[0] -> a test expression
        $extrules{option}[1] -> error message if test fails

       The first part of the array is a perl expression to test the value
       of the option. The test can access this value in the variable
       "$arg". The second part of the array is an error message to display
       when the test fails. The failed value can be integrated by using
       the variable "$arg".

       Config settings with an different prefix than the one given in the
       "readcfg" call are not checked but inserted into %globalcfg and
       %targetcfg.  Prefixed settings keep their prefix in the config

        $targetcfg{'14all*graphsize'}{'target3'} = '500 200'

       "cfgcheck(\@target_names, \%globalcfg, \%targetcfg,

       Checks the configuration read by "readcfg". Checks the values in
       the config for syntactical and/or semantical errors. Sets defaults
       for some options.  Parses the "target[...]" options and filles the
       array @parsed_targets ready for mrtg functions.

       The first three arguments are the same as for "readcfg". The fourth
       argument is an arrayref which will be filled with the parsed target

       "cfgcheck" converts the values of target settings options, e.g.

        options[router1]: bits, growright

       to a hash:

        $targetcfg{'option'}{'bits'}{'router1'} = 1
        $targetcfg{'option'}{'growright'}{'router1'} = 1

       This is not done by "readcfg" so if you don't use "cfgcheck" you
       have to check the scalar variable $targetcfg{'option'}{'router1'}
       (MRTG allows options to be separated by space or ',').


       Checks that the pathname does not contain double path separators
       and ends with a path separator. It uses $MRTG_lib::SL as path
       separator which will be / or \ depending on the OS.

       "log2rrd ($router,\%globalcfg,\%targetcfg)"

       Convert log file to rrd format. Needs rrdtool.


       Returns the time given in the argument as a nicely formated date
       string.  The argument has to be in UNIX time format (seconds since


       Return a string representing the current time.


       Install signalhandlers for __DIE__ and __WARN__ making the errors
       go the the specified destination. If filename is 'eventlog' mrtg
       will log to the windows event logger.


       Returns the time given in the argument formatted suitable for HTTP


       Creates a pid file for the mrtg daemon


       Puts the running program into background, detaching it from the

       "populatecache(\%confcache, $host, $reread, $snmpoptshash)"

       Reads the SNMP variables ifDescr, ipAdEntIfIndex, ifPhysAddress,
       ifName from the host and stores the values in %confcache as

        $confcache{$host}{'Descr'}{ifDescr}{oid} = (ifDescr or 'Dup')
        $confcache{$host}{'IP'}{ipAdEntIfIndex}{oid} = (ipAdEntIfIndex or 'Dup')
        $confcache{$host}{'Eth'}{ifPhysAddress}{oid} = (ifPhysAddress or 'Dup')
        $confcache{$host}{'Name'}{ifName}{oid} = (ifName or 'Dup')
        $confcache{$host}{'Type'}{ifType}{oid} = (ifType or 'Dup')

       The value (at the right side of =) is 'Dup' if a value was
       retrieved muliple times, the retrieved value else.

       "my $confcache = readconfcache($file)"

       Preload the confcache from a file.


       Store the current confcache into a file.


       Store the current confcache into a file.




       "debug($type, $message)"

       Prints the message on STDERR if debugging is enabled for type type.
       A debug type is enabled if type is in array @main::DEBUG.


   Rainer Bawidamann <>

   (This Manpage)


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.