Leonid Shevtsov Leonid Shevtsov - 1 year ago 49
Ruby Question

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

I need to parse a command line like

script.rb <mandatory filename> [options]

with optparse.

Sure I can write some custom code to handle the filename, then pass
to optparse, but maybe there's a simpler way to do it?

EDIT: there's another hacky way to parse such a command line, and that is pass
['--mandatory-filename'] + ARGV
to optparse, then handle the

Answer Source

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

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.