Find a string within a string

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

Hi All,

I am trying to do the following. I have 2 variables
eg. $line='123: ABC/1.0/VAL [111:222:333:444]';
and $cont='ABC/1.0/VAL [111:222:333:444]';
And I have written the following in order to merely identify that the contents of $cont are contained with the contents of $line

if ($head=~/$cont/)
{
print "We have a match\n";
}
else
{
 print "No match\n";

}
[download]

But I keep getting a no match message and can't understand why. I'd really appreciate a response asap as this is seriously holding my work up
Thanx in advance,
Val

update (broquaint): added <code> tags and formatting

Comment on Find a string within a string Select or Download Code

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Re: Find a string within a string by mce (Curate) on Nov 13, 2002 at 12:37 UTC
Hi, Just a quick note: add the line `use re debug;` [download] at the beginning of your script, and it all becomes clear. This will put extra debug information on you regexes, and in your case will show what to match to wich string. This is fairly readable. --------------------------- Dr. Mark Ceulemans Senior Consultant IT Masters, Belgium	[reply] [d/l]
Re: Find a string within a string by Chady (Priest) on Nov 13, 2002 at 11:51 UTC
you are getting "no match" because you are matching against another variable `if ($head=~/$cont/)` which should be `if ($line =~ /$cont/)`. He who asks will be a fool for five minutes, but he who doesn't ask will remain a fool for life. Chady \| http://chady.net/	[reply] [d/l] [select]
Re: Correction to 1st -Find a string within a string by Anonymous Monk on Nov 13, 2002 at 12:02 UTC
Apologies all, error in the code I submitted in initial message The code should read `$line='123: ABC/1.0/VAL 111:222:333:444'; $cont='ABC/1.0/VAL 111:222:333:444'; if ($line=~/$cont/) { print "We have a match\n"; } else { print "No match\n"; }` [download] Thanx, Val	[reply] [d/l]
Re: Re: Correction to 1st -Find a string within a string by rasta (Hermit) on Nov 13, 2002 at 12:11 UTC
That code returns "We have a match". Although I'm think you hould use \Q and \E in comparison to avoid troubles with other strings. So the code should look like this: `$line='123: ABC/1.0/VAL 111:222:333:444'; $cont='ABC/1.0/VAL 111:222:333:444'; if ($line=~/\Q$cont\E/) { print "We have a match\n"; } else { print "No match\n"; }` [download]	[reply] [d/l]
Re: Corection to 1st message entitled -Find a string within a string by rdfield (Priest) on Nov 13, 2002 at 13:00 UTC
Try it using quotemata: `$cont='\QABC/1.0/VAL 111:222:333:444\E';` [download] since you're looking for the literal string. rdfield	[reply] [d/l]
[TIMTOWTDI] Re: Find a string within a string by Zaxo (Archbishop) on Nov 13, 2002 at 20:59 UTC
Since you want an exact match, you can call index instead, and not have to worry about regex metacharacters: `if ( index( $line, $cont) != -1) { print "We have a match\n"; } else { print "No match\n"; }` [download] After Compline, Zaxo	[reply] [d/l]