Perl index() function
The index() function is used to identify or search for the position of a letter or a substring in a string. It will return the position value of the first occurance of the substring within the string.
$index = index(‘iguddy’, ‘gud’);
print $index . “n”;
This will print 1, which is the index value of the start of the substring gud
The index() function is similar to a regular expression call, but without all the overhead of the regex search patterns. It simply returns the index value of the substring if it exists within the string.
Example 1:
Let’s consider you are searching for a particular letter ‘u’ in the following string “iguddy.com”. The following code snippet will help you find the letter ‘u’ in the String “IGuddy.com”
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $letter = ‘u’;
my $result = index($string, $letter);
print “Result: $resultn”;
This program gives you:
Result: 2
Example 2:
The index() function will return -1 if the substring is not present in the actual string.For example, we can look for the letter “A” in the string “iguddy.com”:
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $char = ‘A’;
my $result = index($string, $char);
print “Result: $resultn”;
The program outputs:
Result: -1
Example 3:
If the letter we’re searching for appears more than once in the string, index() return the index of the first occurrence of the letter.
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $char = ‘d’;
my $result = index($string, $char);
print “Result: $resultn”;
This program gives you:
Result: 3
Example 4 :
Instead of searching for a character we can also search for a substring using index() function.
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $substr = ‘gud’;
my $result = index($string, $substr);
print “Result: $resultn”;
This program gives you:
Result: 1
Example 5:
The index() function always return the index of first occurrence of the letter. We can also look for the second occurrence as below,
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $char = ‘d’;
my $offset = 2;
my $result = index($string, $char, $offset);
print “Result: $resultn”;
The program outputs:
Result: 4
Example 6:
Index() in a loop to find out all the occurrence of the substring.
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $char = ‘d’;
my $offset = 0;
my $result = index($string, $char, $offset);
while ($result != -1) {
print “Found $char at $resultn”;
$offset = $result + 1;
$result = index($string, $char, $offset);
}
The above will gives the following output
Found e at 3
Found e at 4
Example 7:
To find the last occurrence of the substring using index() frunction.
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $char = ‘d’;
my $result = rindex($string, $char);
print “Result: $resultn”;
This would produce:
Result: 4
Example 8:
Is there any way of ignoring case in Perl’s index function? The Answer is “Yes” there is a way. Just find below the code snippet,
#!/usr/bin/perl
my $string = ‘iguddy.com’;
my $substr = ‘GUD’;
if (index lc($string),lc($substr) > -1 {
print “Found : Result: $resultn”;
}else{
print “Not Found : Result: $resultn”;
}
This program gives you:
Result: 1
1stenjoydmoment 