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1.14. Trimming Blanks from the Ends of a String

Problem

You have read a string that may have leading or trailing whitespace, and you want to remove it.

Solution

Use a pair of pattern substitutions to get rid of them:

$string =~ s/^\s+//;
$string =~ s/\s+$//;

You can also write a function that returns the new value:

$string = trim($string);
@many   = trim(@many);

sub trim {
    my @out = @_;
    for (@out) {
        s/^\s+//;
        s/\s+$//;
    }
    return wantarray ? @out : $out[0];
}

Discussion

This problem has various solutions, but this is the most efficient for the common case.

If you want to remove the last character from the string, use the chop function. Version 5 added chomp , which removes the last character if and only if it is contained in the $/ variable, " \n " by default. These are often used to remove the trailing newline from input:

# print what's typed, but surrounded by >< symbols
while(<STDIN>) {
    chomp;
    print ">$_<\n";
}

See Also

The s/// operator in perlre (1) and perlop (1) and the "Pattern Matching" section of Chapter 2 of Programming Perl ; the chomp and chop functions in perlfunc (1) and Chapter 3 of Programming Perl ; we trim leading and trailing whitespace in the getnum function in Recipe 2.1 .


Previous: 1.13. Escaping Characters Perl Cookbook Next: 1.15. Parsing Comma-Separated Data
1.13. Escaping Characters Book Index 1.15. Parsing Comma-Separated Data

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