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How can I count the number of occurrences of a sub

Jasmine
Administrator

Jan 19, 2001, 2:52 PM

Post #1 of 1 (1991 views)

How can I count the number of occurrences of a sub	Can't Post

(From the Perl FAQ)

How can I count the number of occurrences of a substring within a string?

There are a number of ways, with varying efficiency: If you want a count of a certain single character (X) within a string, you can use the tr/// function like so:

Code

    $string = "ThisXlineXhasXsomeXx'sXinXit": 
    $count = ($string =~ tr/X//); 
    print "There are $count X charcters in the string";

This is fine if you are just looking for a single character. However, if you are trying to count multiple character substrings within a larger string, tr/// won't work. What you can do is wrap a while() loop around a global pattern match. For example, let's count negative integers:

Code

    $string = "-9 55 48 -2 23 -76 4 14 -44"; 
    while ($string =~ /-\d+/g) { $count++ } 
    print "There are $count negative numbers in the string";

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