NAME
   Cisco::Reconfig - Parse and generate Cisco configuration files

SYNOPSIS
           use Cisco::Reconfig;
           my $config = readconfig("/my/cisco/config");

           use Cisco::Reconfig qw(stringconfig);
           my $config = stringconfig("cisco config", "goes here");

DESCRIPTION
   Cisco::Reconfig makes it easier to write programs to generate changes to
   Cisco configuration files.

   Cisco::Reconfig is a module that parses Cisco router configuration
   files. It doesn't have any real understanding of Cisco configurations so
   it might be useful for other similar configuration languages. It knows
   that nesting is shown by indentation. It knows that "!" means a comment.
   It knows that "no" may proceed a line without changing where that line
   exists in the hierarchy. It doesn't know much else.

   Cisco::Reconfig can be used to modify configurations. The "set()" method
   will check the current configruation and return commands to change it if
   it is other than what is wanted (as passed to the "set()" method).

 DETAILS
   Some of the accessor methods return a special "undef" object instead of
   a proper undef. This is so that code that uses accessors doesn't have to
   be paranoid about undefined values. This "undef" object tests as false
   in boolean context however it is "defined()"ed.

   Methods that return configuration items can return items that represent
   any particular word in the configruation file. For example, with the
   following configuration & code, the return value for the "get()" method
   would represent the word "access-list" in both of the lines:

           ip as-path access-list 111 deny _10993_
           ip as-path access-list 111 permit .*

           $config->get('ip as-path access-list');

   Most of the time you don't need to worry about the fact that the object
   represents a word. Another way to look at it is that the object
   represents a selection of lines from the configuration file. Sometimes
   that selection is a single line. Sometimes it is a block. Sometimes it
   is a few lines that start with the same tokens.

   To look at all the different as-path access lists, the following would
   work:

           $config->get('ip as-path access-list')->all;

   The word "no" is handled specially: it is discarded. Many cisco
   directives start with the word "no". To make the module more usable, the
   word "no" is ignored during parsing. It is kept in the text so, if you
   look for something that might have a "no" in front of it, you'll get a
   hit if the "no" is there or isn't there. For example:

           my (@cdp_disabled);
           for my $context ($config->get('interface')->all(qr{^ether}i)) {
                   my $cdp = $context->get('cdp enable');
                   push(@cdp_disabled, $context)
                           if $cdp =~ /no cdp enable/;
           }

FUNCTIONS
   There is just one function provided: "readconfig()". Readconfig takes a
   single argument: a filename or file handle. It parses the file and
   returns an Cisco::Reconfig object.

MAIN METHODS
   ->get(@designators)
       The "get()" method is the key to looking up items in a configuration
       file. It takes an array of designators as an argument. A designator
       is simply something that identifies a portion of a configuration
       file. For example "('interface')" is a designator for all the
       interfaces and "('ip route')" is a designator for all the static
       routes.

       When multiple designators are specified, they are used for nested
       configuration items. For example, "('router bgp', 'neighbor')" would
       be a designator for all the BGP neighbors. This assumes that there
       is only one "router bgp" defined.

       In array context, "get()" will follow multiple paths to find
       configuration items that match the specification. For example
       "('interface', 'ip address')" would return a list of ip address
       items across multiple interfaces.

       Designators must exactly match words in the configuration. You may
       not abbr anythng.

   ->set(@designators, $newvalue)
       The "set()" method will generate Cisco configuration snippets that
       will modify the configuration of an item. For example, the following
       code:

               my $ser0 = $config->get('interface Serial0');
               print $ser0->set('ip address',
                       'ip address 207.181.198.194 255.255.255.252');

       Will print:

               interface Serial0
                ip address 207.181.198.194 255.255.255.252
               exit

       If the configuration already matches the $newvalue then nothing
       would be printed.

       The designator(s) say what will be modified. This should either be
       represent a line or an entire block. When multiple designators are
       needed, pass them as an anonymous array. The above example could
       also have been written as:

               print $config->set('interface Serial0', 'ip address',
                       'ip address 207.181.198.194 255.255.255.252');

       If no designators are needed, don't pass any. The following is
       nearly the same as the preceeding;

               my $ipaddr = $config->get('interface Serial0', 'ip address');
               print $ipaddr->set( 'ip address 207.181.198.194 255.255.255.252');

       When providing code snippets to "set()", indent blocks just like
       Ciscos do when they display their configuration. For example, the
       following:

               print $config->set("ip access-list extended all-addresses", <<END);
                       ip access-list extended all-addresses
                        permit ip any any
                       !
               END

       Will print the following if the access list ins't already set as
       listed:

               ip access-list extended all-addresses
                permit ip any any
               exit

       When modifying a block, include the configruation line that starts
       the block in the replacement text. For example, when setting an
       entire interface, provide the entire block:

               print $config->set('interface Serial0',<<END);
                       interface Serial0 point-to-point
                        ip address 219.22.221.3 255.255.255.252
                        bandwidth 3022
                       !
               END

   ->all($regex)
       The "all()" method can be used to expand and select configuration
       items.

       For example, to make sure that all loopback interfaces use a netmask
       of 255.255.255.255, use the following:

               for my $loop ($config->get('interface')->all(qr{^Loop})) {
                       my $ip = $loop->get('ip address');
                       next unless $ip->text =~ /\A\s*ip address (\S+) \S+\s*\Z/;
                       print $ip->set(undef, "ip address $1 255.255.255.255");
               }

       The $regex paramater is optional.

ACCESSOR METHODS
   ->single()
       Cisco::Reconfig objects may represent any word in a configruation
       file. For example the word "address" in the following is represented
       by an object that would be returned by the code that follows.

               interface Loopback0
                ip access-group 151 in
                ip address 218.28.41.38 255.255.255.255
               !

               my $address_word = $config->get('interface Loopback0', 'ip')
                       ->all(qr{^address});

       "single()" answers the question: does this Cisco::Reconfig object
       uniquely specify a single point in the configuration? In the example
       above, the object for word "ip" (above) does not but the object for
       the word "address" does.

       "single()" returns an object (representing the last word on the
       line) or undef.

   ->zoom()
       "zoom()" is the same as to "single()" except that it will always
       return a valid Cisco::Reconfig object.

   ->endpt()
       Returns an Cisco::Reconfig object representing the last word on a
       configuration line that could follow from the current ZYZ object.
       When there are multiple possibilities the object picked is nearly
       random.

   ->next()
       "next()" returns an Cisco::Reconfig object representing the last
       word on the suceeding line of the current configuration block.

       When used at the beginning of a block, it returns the last word of
       the first line in the block.

   ->context()
       Returns the configuration object that represents the surounding
       context.

               # returns the "undefined" object
               $config->context

               # returns $config
               $config->get('interface Loopback0')->context

               # returns $config->get('interface Loopback0')
               $config->get('interface Loopback0', 'ip address')->context

       "context()" always returns a configuration object.

   ->subs()
       For Cisco::Reconfig objects that represent a word in a line that
       introduces a block of configuration items (such as most "interface"
       lines), the "subs()" function returns an Cisco::Reconfig object that
       represents the contents of the block.

       If the Cisco::Reconfig object in question does not represent the
       start of a configuration block, the "undefined" object is returned.

   ->kids()
       For Cisco::Reconfig objects that do not uniquely specify a single
       line (ie: "! -"single()>), the ->kids() method will return an array
       of objects representing the possible following words.

       If there is only one possibility, that one possibility is returned.

       If the Cisco::Reconfig object represents the last word on a
       configuration line then that word is returned.

MISCELLANEOUS METHODS
   ->text()
       Returns the text from the original configuration file (in original
       order) of all of the lines that could follow from the current
       Cisco::Reconfig object.

       When the invoking Cisco::Reconfig object represents a single line
       "text()" returns that line. When the invoking Cisco::Reconfig object
       represents a block "text()" returns the entire block. When the
       Cisco::Reconfig object represents a word with multiple possible
       completions, "text()" returns all the completions.

   ->alltext()
       Returns the text from the original configuration file of all the
       lines that could follow from the current Cisco::Reconfig object and
       all lines that are introduced by the current object.

       To get the text of all interface definitions in their entirety, use;

               $config->get('interface')->alltext

   ->setcontext()
       Returns an array of configuration lines that define the block
       surrounding the invoking object.

   ->unsetcontext()
       Returns an array of the word "exit" repeated as many times as
       nessasary to undo a "setcontext()".

   ->block()
       Returns true if the object represents a whole configuration block.

TWEAKS
   Some cisco configurations have a minus one indent beginning with the
   "class" keyword. This exception is matched and handled. To change the
   regex for what is accepted for a minus-one indent, override
   $Cisco::Reconfig::allow_minus_one_indent to a new regex. Set to "undef"
   to disable this override.

   Some cisco configurations have a plus one indent beginning with the
   "service-index" keyword. This exception is matched and handled. To
   change the regex for what is accepted for a plus-one indent, override
   $Cisco::Reconfig::allow_plus_one_indent to a new regex. Set to "undef"
   to disable this override.

   If you encounter other broken indents, please let the maintiner know. If
   it can be handled with the above overrides, do so. If it cannot, you can
   change $Cisco::Reconfig::bad_indent_policy to "WARN" or "IGNORE". The
   default behavior is to die.

OVERLOADING
   Two operators are overloaded: boolean tests and stringification.
   Cisco::Reconfig objects booleanify as true if they are the special
   undefined objects. Cisco::Reconfig objects stringify as their text
   lines.

CAVEATS
   Since Cisco::Reconfig doesn't really understand Cisco configuration
   files it can't know things that you might think it should.

   For example, it doesn't know that "interface Serial0" is the same as
   "int ser 0" nor even "interface Serial 0". Be very careful about where
   Cisco's actually put spaces and where they don't.

   No attempt has been made to make this module particularly fast or
   efficient for the computer.

   Cisco::Reconfig objects don't automatically garbage collect themselves
   because they are highly self-referrential.

LICENSE
   Copyright (C) 2002-2010 David Muir Sharnoff <[email protected]>
   Copyright (C) 2011-2012 Google, Inc. This module may be licensed on the
   same terms as Perl itself.

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