珀尔 | index()函数

此函数返回字符串（或文本）中给定子字符串（或模式）第一次出现的位置。我们可以指定起始位置。默认情况下，它从头开始搜索（即从索引零开始）。

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.

示例 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";

输出：

Position of 'the' in the string: 10

示例 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";

输出：

Position of 'Geeks' in the string: -1

这里，在第二个示例中，位置设置为“3”，即开始搜索的起始索引是从第 3 个位置开始。因此，在字符串中找不到子字符串。