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Ruby: Printing N things per line from a list

Page created: 2025-07-24

back to ruby

For some reason, I keep having a need to write Ruby scripts that output lists in reasonably-sized columns.

The key is to use Ruby’s Array slice() method to get the list in chunks.

This example doesn’t print pretty aligned columns, it just prints a certain quantity of items per line:

require 'json'

# Read a JSON file with a couple thousand items in an array:
jsonf = File.read('data-ordered-emoji.json')
list = JSON.parse(jsonf)

# Print in columns of 30 items

col=30
i=0

while i < list.length
    joined = list.slice(i, col).join(" ")
    puts(joined)
    i += col
end

As you can see, slice() allows you to specify a length in the second parameter which extends beyond the length of the list without complaint, which is very handy.