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Perl script to replace a line after finding a previous line

Hi all,

At the moment I have a flat file which is being used by a few people. I want a script to remotely change the file, so I can start logging who is doing what.

At this point here is one requirement I am trying to develop. We have text blocks who pretty much look like this:

---------------------- C001

$$var1=Source
$$var2=Target
$$var3=2

---------------------- C006

$$var1=Source
$$var2=Target
$$var3=3

In this text block I first want to find C001 and afterwards change $var3. Thing is, I don't want to change all $var3's.

This is my code so far;

Code:

        open(PARAM, "<be_cycle3b.prm") or die ("Kan parameter bestand niet openen.");



        my @dat_param = <PARAM>;



        foreach my $regel (@dat_param){



                if( $regel =~ /^-+ +$workflow/g ){



                        print $regel;



                        foreach (my $regel_n = @dat_param) {



                                print " \n regel_n: " , $regel_n  , " \n ";



                                if( $regel_n =~ /^$param/ ){

                                        

                                        print " foreach regel_n: ",$param;



                                        print $regel_n;

                                }

                        }





                }



        }



        close(PARAM);

I have not come to the point of changing $$var3. Even trying to read the line with $var3 is not possible yet.

Here are the used variables:

$workflow (C001 as in example given)

$param = $$var3

I hope this is somewhat clear. I try to find $param for the right $workflow and change that. Can you help me to find $$var3 and change that?

Much appreciated.

There is more than one way to do it

My recommendation is to use a state structure, since this makes it fairly simple to see what is going on.

Code:

        open(PARAM, "<be_cycle3b.prm") or die ("Kan parameter bestand niet openen.");

        

        my @dat_param = <PARAM>;

        my $state = 0;

        foreach my $regel (@dat_param){

                if( $regel =~ m/^-+/ ){

                        if($regel =~ m/$workflow/){

                                #You found the right section

                                $state = 1;

                        }

                        else{

                                #You are in a wrong section

                                $state = 0;

                        }

                }

                if($state == 1 and $regel =~ m/^$param/){

                        # You have now read the right line,

                        # so do something useful below.

                        print "$regel";

                }

        }

This way you don't end up processing the wrong lines.

As for how to change $var3, just remember that, if $var = 'a' you can access $a as $$var, but read the perlreftut and/or perlref manpages for the complete story.

Good luck