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Perl | index() Function

  • Last Updated : 25 Jun, 2019
Geek Week

This function returns the position of the first occurrence of given substring (or pattern) in a string (or text). We can specify start position. By default, it searches from the beginning(i.e. from index zero).

Syntax:
# Searches pat in text from given index
index(text, pat, index)

# Searches pat in text
index(text, pat)

Parameters:

  • text: String in which substring is to be searched.
  • pat: Substring to be searched.
  • index: Starting index(set by the user or it takes zero by default).

Returns:
-1 on failure otherwise Position of the matching string.



Example 1:




#!/usr/bin/perl
  
# String from which Substring 
# is to be searched 
$string = "Geeks are the best";
  
# Using index() to search for substring
$index = index ($string, 'the');
  
# Printing the position of the substring
print "Position of 'the' in the string: $index\n";
Output:
Position of 'the' in the string: 10

Example 2:




#!/usr/bin/perl
  
# String from which Substring 
# is to be searched 
$string = "Geeks are the best";
  
# Defining the starting Index
$pos = 3;
  
# Using index() to search for substring
$index = index ($string, 'Geeks', $pos);
  
# Printing the position of the substring
print "Position of 'Geeks' in the string: $index\n";
Output:
Position of 'Geeks' in the string: -1

Here, in the second example the position is set to ‘3’, i.e. the starting index from where searching is to begin is from 3rd position. Hence, the substring is not found in the String.

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