Question

This is my first Perl script. Ever:

#!/usr/bin/perl

if ($#ARGV < 1) { die("usage: <size_in_bytes> <file_name>\n"); }

open(FILE,">" . $ARGV[0]) or die "Can't open file for writing\n";

# you can control the range of characters here
my $minimum = 32;
my $range = 96;

for ($i=0; $i< $ARGV[1]; $i++) {
    print FILE chr(int(rand($range)) + $minimum);
}

close(FILE);

Its purpose is to generate a file in a specified size filled with random characters.

It works but it is pretty slow. It takes a few seconds to write a 10MB random file.
Does anyone have suggestions/tips on how to make it faster/better? Also feel free to point out common newbie mistakes.

Answer 1

1. You could ask rand to create more than one value for you each time you call it.
2. Collect several characters together before calling print. Printing one character at a time is inefficient.

 

for (my $bytes = 0; $bytes < $num_bytes; $bytes += 4) {
    my $rand = int(rand($range ** 4));
    my $string = '';
    for (1..4) {
        $string .= chr($rand % $range + $minimum);
        $rand = int($rand / $range);
    }
    print FILE $string;
}