http://qs1969.pair.com?node_id=1152125


in reply to Update config file parameters

I understand that your config file is probably plain text, but here's an option using Data::Dumper and require.

Start with a configuration format, like a HASH: 
perl -MData::Dumper -e '
  $conf = {
    DEVICE => 'eth0',
    ONBOOT => 'yes',
    BOOTPROTO => 'static',
    TYPE   => 'Ethernet',
    IPADDR => '10.9.0.200',
    NETMASK   => '255.255.0.0',
    GATEWAY   => '10.9.1.254',
  };
  open( $fh, ">", "monkConfig.txt" ) or die;
  print $fh Data::Dumper->Dump([$conf],["config"]);
'

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Creates a file with this format: 
$config = {
            'TYPE' => 'Ethernet',
            'ONBOOT' => 'yes',
            'NETMASK' => 255.255.0.0,
            'GATEWAY' => 10.9.1.254,
            'DEVICE' => 'eth0',
            'IPADDR' => 10.9.0.200,
            'BOOTPROTO' => 'static'
          };

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Then use require to access the data: 
perl -le 'require "monkConfig.txt";
  print $config->{'TYPE'};
'

__output__
Ethernet

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...then redo the Dump to write changes back to file. Yeah, probably a bit more tedious then Tie::File, but imagine the possibilities!

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Re^2: Update config file parameters
by afoken (Chancellor) on Jan 07, 2016 at 21:12 UTC
    here's an option using Data::Dumper and require

    Please DON'T use this "solution"!

    This opens a HUGE vulnerability, simply because require $filename;, use $filename;, do $filename;, and eval $filecontent; all treat the configuration file as executable code.

    See also Re^2: conf file in Perl syntax, Re^2: Storing state of execution.

    Or just imagine someone successfully executing echo 'system "/bin/rm -rf /";' >> monkConfig.txt before root executes perl -le 'require "monkConfig.txt";'.

    Also, use and require load each file only once, unless you start messing with %INC.

    Alexander

    --
    Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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      Wow, I did not know require would execute the content of the file.

      Very good to know. I am glad you found my post and corrected it.

      Thanks!
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        I did not know require would execute the content of the file.

        Think about it: How else could require and use (which is just require wrapped in a BEGIN block, and optionally a call to an import method) load and initialise a perl module? How would module Foo load a module Bar that it depends on, if not by executing use or requrie in Foo when the main program requires or uses Foo?

        Alexander

        --
        Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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