searching for a substring in a string

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

Hello Monks,

In a file I have content like:

myFiles = test02-01-2005.txt ; hello27-12-2004.txt;

I open the file and hunt for the string "myFiles" and want to update the file starting with "test" to "test29-01-05.txt"

My question is how do I search for the string that starts with "test" and ends with ".txt" since it can consider the whole string "test02-01-2005.txt; hello27-12-2004.txt" as starting with test and ending with .txt.

How do I tell regex to stop at the first .txt when it sees it?

Notice the ";" sometimes are placed after a space and sometimes placed without a space after the filename.

If I do something like:


open ( FH, "p.txt" );
my @output = <FH>;
close ( FH );

#find the line which has "myFiles" in it
my @line = grep ( /myFiles/ ), @output;

#hopefully I should only one line back
my $i = $line[0];


#will this work?
$i =~ s/.*(test.*\.txt).*/test29-01-05\.txt/
[download]

Thank you

Comment on searching for a substring in a string Download Code

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Re: searching for a substring in a string by dragonchild (Archbishop) on Feb 02, 2005 at 17:23 UTC
`$i =~ s/.(test.?\.txt).*/test29-01-05\.txt/` [download] Note the question-mark. Being right, does not endow the right to be rude; politeness costs nothing. Being unknowing, is not the same as being stupid. Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence. Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.	[reply] [d/l]
Re^2: searching for a substring in a string by Ardemus (Beadle) on Feb 02, 2005 at 18:58 UTC
To expand upon the solution: `$string = "Cats and dogs shouldn't eat hot dogs"; $string =~ m/.dogs/; # Greedy Quantifier $string =~ m/.?dogs/; # Lazy Quantifier` [download] Greedy quantifiers gobble up every character they can, then back off until a match is made. Lazy quantifiers find as little as possible, then expands what it matches until it can match the rest of the regex. The first search matches the entire string, while the second search matches, "Cats and dogs". If you're getting into Regex, I'd recommend 'Mastering Regular Expressions'. It will provide some invaluable insights into these sorts of things. Ardemus "This, right now, is our lives."	[reply] [d/l]
Re^2: searching for a substring in a string by Anonymous Monk on Feb 02, 2005 at 17:43 UTC
Thank you If I want to update the line in the same file, how do I do it without just appending to the last line. Is there a way I can just update a single line wherever it exists in the file to the same location? Thanks	[reply]
Re^3: searching for a substring in a string by punch_card_don (Curate) on Feb 02, 2005 at 18:47 UTC
Clunky, but clear, change that line in the array and re-write the file: `open ( FH, "p.txt" ); my @output = <FH>; close ( FH ); open ( FH, ">p.txt" ); for $i (0 ..#@output) { if ($output[$i] =~ /.(test.\.txt)./) { $output[$i] =~ s/.(test.\.txt)./test29-01-05\.txt/ last; } for $i (0 ..#@output) { print "$output[$i]"; } close ( FH );` [download] Forget that fear of gravity, Get a little savagery in your life.	[reply] [d/l]
Re^4: searching for a substring in a string by Anonymous Monk on Feb 02, 2005 at 20:20 UTC
Re^3: searching for a substring in a string by kutsu (Priest) on Feb 02, 2005 at 17:54 UTC
I don't know if I'm reading you right but: `perl -p -i.bkup -e "s/.(test.?\.txt)./test29-01-05\.txt/;" p.txt`, might do what you want. (see perlrun) "Cogito cogito ergo cogito sum - I think that I think, therefore I think that I am."* Ambrose Bierce	[reply] [d/l]