Perl - File Slurping

A common idiom in Perl 5 is "slurping".  Slurping is the process of reading a file into an array, split by line breaks.  You can then iterate over the array and perform an operation on each line.  This is the basic input mechanism I use to process all sorts of data/text files.

The basic slurp goes like this...

Open a file in read mode and assign it a file handle:

open(FILE, 'foo.txt') or die $!;

Read (slurp) the file into an array of lines (splitting the file on newlines):

@file = <FILE>;

You can then process the array in a foreach loop and "Un-slurp" (De-slurp?) it back to the file system like this...

Now we have an array which we can iterate through and do whatever we want with each line:

foreach (@file) {
    # do something here
}

Re-open the file in overwrite mode:

open(FILE, '>foo.txt') or die $!;

Print the contents of the array back to the file:

print FILE @file;

The following script shows some slurping in a action. This script will read a file named "foo.txt" and replace all intances of "foo" with "bar"

#!/usr/bin/perl


replace('foo.txt', 'foo', 'bar');


sub replace {
    ($filename, $original, $substituted) = @_;

    open(FILE, $filename) or die $!;
    @file = ;

    foreach (@file) {
        s/$original/$substituted/g;
    }

    open(FILE, '>foo.txt') or die $!;
    print FILE @file;
}