How to parse an argument without a name with Ruby’s optparse

August 6, 2023 by Tarik

First parse! with optparse, then scan the ARGV and raise if ARGV is empty. Like so:

op.parse!
filename = ARGV.pop
raise "Need to specify a file to process" unless filename

The mandatory filename will not be processed by the OptionParser and will be left for you in ARGV – if it’s not there, just raise manually.