matching + character in a file

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

In this code i am having a hard time matching "a+b" as an argument. If i insert "a\\+b" as an argument it works. I am wondering if there is another way around this so that it works with "a+b" as an argument.


use strict;

my $var1 = $ARGV[0];  
print $var1."\n";

open(IN, "temp.mine") or die "Error opening temp.mine\n";
while(<IN>) {
    my $line = $_;
          print "input = $line\n";        
    if($line =~ /$var1/m) {
        print "found \n";
        close(IN) or die "Error closing file\n";
        exit 0;
    }
}

close(IN) or die "Error closing temp.mine\n";
print "not found  \n";


#contents of file temp.mine
#a+b
[download]

i am working on a larger program where i am having an error due to the above problem. Please if anyone knows a way i can match this without changing my input argument or the temp.mine file let me know asap. Thanks Waris

Comment on matching + character in a file Download Code

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Re: matching + character in a file by tachyon (Chancellor) on Aug 07, 2001 at 01:05 UTC
Please have a look at all the answers you got at matching the + character. In short do either of these: `$var1 = quotemeta $var1; # do this before you use it in the regex or if ($line =~ /\Q$var1\E/m)` [download] Either of these escape all regex metachars and should be considered mandatory if you want to avoid problems interpolating variables into regexes. PS Don't do both at the same time - it is either or! cheers tachyon print quotemeta 'a+b';	[reply] [d/l]
Re: matching + character in a file by runrig (Abbot) on Aug 07, 2001 at 01:08 UTC
See quotemeta: `$var1 = quotemeta($var1); ...etc.` [download]	[reply] [d/l]
2 small things by dga (Hermit) on Aug 07, 2001 at 02:54 UTC
`1. print $var1."\n"; ... 2. if($line =~ /$var1/m) ...` [download] 1. You might want to `print "$var1\n"; #similar look and obvious function OR print $var1, "\n"; #efficiency` [download] The first looks like your other print usages and does the most obvious thing (prints the variable and a newline) The second is a bit more efficient because there is no concatenation of 2 strings followed by a print of the result. print is a list operator which pops out its arguments one after the other, in this case $var1 followed with no space by "\n" 2. In the code sample (with that while) you should only get one line so I dont see a need for the /m modifier do do multiline matching.	[reply] [d/l] [select]
Re: matching + character in a file by mischief (Hermit) on Aug 07, 2001 at 15:00 UTC
If all you're doing is trying to match a '+', another way to do this would be with the `index` function: `#!/usr/bin/perl -w use strict; my $a = '123a+b456'; print "found\n" unless index($a, 'a+b') == -1;` [download] I'm not entirely sure how efficient that is, though (but I have a suspicion it's more efficient than attempting a full regex match).	[reply] [d/l] [select]