Given a file like this, that has rows of numbers in it without anything, but a single space in between the numbers. Our task is to count how many times each digit appears.

examples/data/count_digits.txt

23 34 9512341
3 34 2452345 5353 67 22
42136357013412
42 5 65 64 

Our expected output looks like this:

0 1
1 5
2 9
3 11
4 9
5 8
6 4
7 2
8 0
9 1

Tools for Perl 5

• The Perl 5 tutorial in general.
• Perl 5: shift from @ARGV
• Perl 5: open a file for reading or die.
• Perl 5: Arrays
• Perl 5: chomp, remove trailing newlines.
• Perl 5: split, to cut a string into pieces.

Tools for Ruby

• Ruby: ARGV for command line parameters
• Ruby: Open file and read content
• Ruby: Arrays
• Ruby: Iterate over elements of a an array

Solutions

• Perl 5 count digits
• Ruby: count digits
• Groovy: count digits