String match issue 2

[whn]

Please take a look at the small sample code here.
I just don't understand why it actually finds a match!!

#!/usr/bin/perl -w

my $str = "group=1,101,102";
my $ip = "1.1.1.1";
if($str =~ /$ip/) {
  print "The string contains this IP!!\n"
}
else {
  print "The string does not contain this IP!!\n"
}
print "String: #$str#\n";
print "    IP: #$ip#\n";
exit;

Sample run:

./test.pl 
The string contains this IP!!
String: #group=1,101,102#
    IP: #1.1.1.1#

Thanks for your time and help!!

 

[yelworcm]

The periods need to be escaped. Right now, they are matching any character (which includes , 0 ,). Try it with this:

#!/usr/bin/perl -w

my $str = "group=1,101,102";
my $ip = '1\.1\.1\.1';
if($str =~ /$ip/) {
  print "The string contains this IP!!\n"
}
else {
  print "The string does not contain this IP!!\n"
}
print "String: #$str#\n";
print "    IP: #$ip#\n";
exit;

Note, i have switched the double quotes to single quotes, so I did not have to escape the escape character. I have not tested this, so feel free to come back with problems.

 

[prex1]

The dot stands for 'any character' in the regex. One way to solve this is to disable the metacharacters by prepending [tt]\Q[/tt] : [tt]if($str =~ /\Q$ip/) {[/tt]

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[MillerH]

Use \Q...\E to escape regular expression special characters, like the any character '.'

Also use word boundaries \b so that you don't match a substring like 1.1.1.100

use strict;
use warnings;

my $str = "group=1,101,102";
my $ip = "1.1.1.1";

if ($str =~ /\b\Q$ip\E\b/) {
	print "The string contains this IP!!\n"

} else {
	print "The string does not contain this IP!!\n"
}

print "String: #$str#\n";
print "    IP: #$ip#\n";
exit;

- Miller