The simplest perl Multi Line matching.

dannyd has asked for the wisdom of the Perl Monks concerning the following question:

Hello monks,

I have been trying to match the pattern below, but have been greatly unsuccessful. There are 5 lines in the Output

--------------------------------------------------------------
Perl Progress
--------------------------------------------------------------
 
dannyd@cli>
[download]

This is the code I have been trying,

#!/usr/bin/perl

open (FH, "test.txt");
while (<FH>)
{
    print "Match!!\n" if ($_ =~ /^-+\nBG/ms);
}
close (FH);
[download]

I am able to match any one of the lines, but when I try to match the next one using the same regular expression, It fails, please help me figure out why this is happening

And any good material to read on multi line matching would also be highly appreciated

Comment on The simplest perl Multi Line matching. Select or Download Code

Replies are listed 'Best First'.
Re: The simplest perl Multi Line matching. by Anonymous Monk on Feb 08, 2011 at 08:03 UTC
you're not error checking, `use autodie;` you're reading the file, line-by-line, think about it :) start with perlintro, add `use re 'debug';`, perlretut/Pattern Matching, Regular Expressions, and Parsing, YAPE::Regex::Explain	[reply]
Re^2: The simplest perl Multi Line matching. by dannyd (Sexton) on Feb 08, 2011 at 08:54 UTC
Ok Thanks, that was very cunning, I just thought about that after reading your post. I'm going through the links you sent. Ive modified it to this, seems to work fine, please tell me if you have anything else to say about the code. `#!/usr/bin/perl my $newstr = ''; open (FH, "test.txt") \|\| die "Could not open file.\n"; while(<FH>) { $newstr = $newstr.$_; print "!!\n" if ($newstr =~ /^-+\nPerl Progress\n-+\n\s\ndannyd\@c +li>\s$/m); } close (FH);` [download] Thanks a lot by the way, in my opinion this got solved super fast!!	[reply] [d/l]
Re^3: The simplest perl Multi Line matching. by CountZero (Bishop) on Feb 08, 2011 at 22:06 UTC
`my $newstr = '';` [download] Altough it is not "wrong" there is no reason at all to initialize a lexical variable to the empty string (or zero) as the `my` takes care of creating a brand new "empty" variable with the value of `undef`, empty string or zero (depending on how you look at it). CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l] [select]
Re: The simplest perl Multi Line matching. by elwarren (Priest) on Feb 08, 2011 at 15:45 UTC
See Perl FAQ 6 Regex: How can I pull out lines between two patterns that are themselves on different lines?	[reply]


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