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Re: multi-line parsing

by jethro (Monsignor)
on Mar 31, 2009 at 18:47 UTC ( #754501=note: print w/replies, xml ) Need Help??

in reply to multi-line parsing

Your problem is that you are reading the file line by line but expect three lines in your search pattern

There are a lot of ways you could do this, one would be to use a state machine. It uses a variable that notes which state it is in and depending on the next line switches to an appropriate state.

In this case state 1 means "I'm at the line after the first line I'm looking for" and state 2 means "I'm after the second line which followed the first line, expecting the number now"

#!/usr/bin/perl use strict; use warnings; my @array=(); open (INF, "$file"); my $state= 0; while (<INF>){ if ($state==0) { if (/^First line of text$/) { $state=1; } next; } if ($state==1) { if (/^second line of text$/) { $state=2; } elsif (/^First line of text$/) { $state=1; } else { $state=0; } next; } if ($state==2) { if (/^in the third line I have (\d*\.\d*)/) { push(@array,$1); $state=0; } elsif (/^First line of text$/) { $state=1; } else { $state=0; } next; } }

Note I used ^ and $ to denote line begin and end in the patterns so that the full lines must correspond to the pattern, not only a part of a line. Also used strict and warnings.

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