John Hawthorn

QR Codes on the Command Line

I recently got a new Android phone and found that QR codes were a cool, quick way to transfer URLs and text. There were a couple cases where I found it useful to automatically generate the QR code and display it on my laptop screen for me to scan with my phone.

Instead of generating the codes as a png with an existing program and opening them in my image viewer, I figured I’d hack together a quick ruby script to do the job. Here’s the result.

qrcli screenshot

It encodes either its first argument or standard input to a QR code and prints that directly to the terminal with a small white border. I’ve found that the ZXing scanner program has a very easy time reading this. It automatically choses the smallest size of code which can fit the input, and has the lowest setting for error recovery.

Here’s the script:

#!/usr/bin/env ruby require 'rubygems' require 'rqrcode' LEVEL = 'l' BLACK = "\e[40m" WHITE = "\e[107m" DEFAULT = "\e[49m" SPACER = " " text = ARGV[0] || # make a qr code of the smallest possible size qr = nil (1..10).each do |size| qr =, :level => LEVEL, :size => size) rescue next break end width = qr.modules.length puts WHITE + SPACER * (width + 2) + BLACK width.times do |x| print WHITE + SPACER width.times do |y| print (qr.is_dark(x,y) ? BLACK : WHITE ) + SPACER end puts WHITE + SPACER + DEFAULT end puts WHITE + SPACER * (width + 2) + BLACK

This requires the rqrcode gem and a terminal supporting ANSI color escape sequences (which is pretty much everything).