# Minimalistic command line option parsing via -s **URL:** \ **Category:** Ruby\ **Created:** [September 6, 2007, 5:36pm UTC](https://www.ruby-forum.com/t/minimalistic-command-line-option-parsing-via-s/113956 "2007-09-06T17:36:23Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Bil\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/848f3c/32.png) [@Bil\_K](https://www.ruby-forum.com/u/Bil_K)\ **Post date:** [September 6, 2007, 5:36pm UTC](https://www.ruby-forum.com/t/minimalistic-command-line-option-parsing-via-s/113956/1 "2007-09-06T17:36:23Z")
Hi, I know, I’m slow, but I finally figured out the minimalistic command line options parsing that zenspider et al use in utilities like flog and sow (the gem skeleton generator that comes with Hoe). Consider, for example, #!/usr/bin/env ruby -s $r ||= false if defined? $h then puts “usage: #{File.basename $0}” puts " -h this usage message" puts " -r recursive" end puts “Recursive option: #$r” The secret sauce is the ‘-s’ option passed to the interpreter, which according to the PickAxe indicates, “Any command-line switches found after the program filename, but before any filename arguments or before a --, are removed from ARGV and set to a global variable named for the switch.” Later, ---
**Author:** ![Bil\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/848f3c/32.png) [@Bil\_K](https://www.ruby-forum.com/u/Bil_K)\ **Post date:** [September 6, 2007, 5:56pm UTC](https://www.ruby-forum.com/t/minimalistic-command-line-option-parsing-via-s/113956/2 "2007-09-06T17:56:30Z")
Bil K. wrote: > $r ||= false > which according to the PickAxe indicates, “Any command-line switches > found after the program filename, but before any filename arguments > or before a --, are removed from ARGV and set to a global variable > named for the switch.” It’s nice to have that for very short scripts, but for about 50 LOC you can paste in an options parser that permits --foo style options, -xyz as an alias for “-x -y -z”, option arguments, argument conversion procs and defaults, “-x123” as an alias for “-x 123”, and even a way to interpret “-v -v -v” as thrice verbose. One thing you can’t have is _optional_ arguments to options (e.g. an option that takes 0 or 1 arguments). [http://redshift.sourceforge.net/argos.rb](http://redshift.sourceforge.net/argos.rb) ---
**Author:** ![Bil\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/848f3c/32.png) [@Bil\_K](https://www.ruby-forum.com/u/Bil_K)\ **Post date:** [September 6, 2007, 11:52pm UTC](https://www.ruby-forum.com/t/minimalistic-command-line-option-parsing-via-s/113956/3 "2007-09-06T23:52:27Z")
On Sep 6, 2007, at 11:55 AM, Joel VanderWerf wrote: > It’s nice to have that for very short scripts, but for about 50 LOC > you can paste in an options parser that permits --foo style > options, -xyz as an alias for “-x -y -z”, option arguments, > argument conversion procs and defaults, “-x123” as an alias for “-x > 123”, and even a way to interpret “-v -v -v” as thrice verbose. One > thing you can’t have is _optional_ arguments to options (e.g. an > option that takes 0 or 1 arguments). A really nice tool I stumbled on while e-stalking Ara Howard (hehe sorry) was his main library (gem install main). He’s got some example code of it on his site, and it makes options really really easy! Ari -------------------------------------------| Nietzsche is my copilot ---
**Author:** ![Bil\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/848f3c/32.png) [@Bil\_K](https://www.ruby-forum.com/u/Bil_K)\ **Post date:** [September 7, 2007, 2:28am UTC](https://www.ruby-forum.com/t/minimalistic-command-line-option-parsing-via-s/113956/4 "2007-09-07T02:28:38Z")
Hi, At Fri, 7 Sep 2007 00:30:05 +0900, Bil K. wrote in [ruby-talk:267895]: > I know, I’m slow, but I finally figured out the minimalistic > command line options parsing that zenspider et al use in utilities > like flog and sow (the gem skeleton generator that comes with Hoe). and mkconfig.rb and win32/{mkexports,resource}.rb too. > Consider, for example, > > #!/usr/bin/env ruby -s Multiple words in shebang line may not work as you expect. ---
**Author:** ![Bil\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/848f3c/32.png) [@Bil\_K](https://www.ruby-forum.com/u/Bil_K)\ **Post date:** [September 7, 2007, 1:22am UTC](https://www.ruby-forum.com/t/minimalistic-command-line-option-parsing-via-s/113956/5 "2007-09-07T01:22:34Z")
Ari B. wrote: > A really nice tool I stumbled on while e-stalking Ara Howard (hehe > sorry) was his main library (gem install main). He’s got some example > code of it on his site, and it makes options really really easy! Just took a look at it… very powerful. It handles arguments (things without – or -) as well as options. It’s also fairly complex, and not the sort of thing you paste into a small script (almost 2000 lines). Main looks like more of a complete framework for CLI (possibly like the commandline gem–has anyone compared these two?). By contrast, argos does just one thing: turn an arg string into a hash, based on a spec. ---
**Author:** ![Bil\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/848f3c/32.png) [@Bil\_K](https://www.ruby-forum.com/u/Bil_K)\ **Post date:** [September 7, 2007, 3:03am UTC](https://www.ruby-forum.com/t/minimalistic-command-line-option-parsing-via-s/113956/6 "2007-09-07T03:03:40Z")
On Sep 6, 2007, at 10:30 AM, Bil K. wrote: > $r ||= false > which according to the PickAxe indicates, “Any command-line switches > found after the program filename, but before any filename arguments > or before a --, are removed from ARGV and set to a global variable > named for the switch.” I talk about this some in the summary for this quiz as well: [http://www.rubyquiz.com/quiz133.html](http://www.rubyquiz.com/quiz133.html) James Edward G. II