Today I Learned

Ruby print to replace contents on same line

In Ruby, the print command can be used with the '\r' (carriage return) character to bring the cursor back to the beginning of the printed line, so that the next print call will replace the contents already outputted to that line. This is a very useful tool for printing status updates in a CLI script. For example:

print "#{index} done. Progress: %.2f%" % (index.to_f / items * 100).round(2) + "\r" if (index % 10) == 0

This will print and replace a line in STDOUT to report the status of a list of items being processed by a function, like so:

200 done. Progress: 15%

Typewriters still hold a lasting impact on modern-day computing!