# Command-line option parsing
**URL:** https://rubytalk.org/t/command-line-option-parsing/23639
**Category:** ruby-talk
**Created:** [27 December 2005 23:37 UTC](https://rubytalk.org/t/command-line-option-parsing/23639 "2005-12-27T23:37:53Z")
**Posts on this page:** 18
**Page:** 1
### Author:  [@Eric\_J\_Roode](https://rubytalk.org/u/Eric_J_Roode)
#### Post date: [27 December 2005 23:37 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/1 "2005-12-27T23:37:53Z")
Greetings,
I'm new to ruby (from Perl). I notice there are several command-line
options parsing modules. The two that stuck out were GetoptLong and
OptionsParser. GetoptLong suffers from being "the same old Getopt".
OptionsParser claims to be "more advanced and more ruby-like", but has
extremely poor documentation.
Are these the best two modules out there? Is there an emerging
"standard" module? (In Perl, Getopt::Long is by far the most commonly-used
module).
(I apologize if this is a FAQ; I read the FAQ and did a google scan of past
articles. Most of what I found was authors announcing their own options-
parsing modules).
Thanks in advance,
> **···**
>
> --
> Eric Roode
---
### Author:  [@Lou\_Vanek](https://rubytalk.org/u/Lou_Vanek)
#### Post date: [28 December 2005 00:09 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/2 "2005-12-28T00:09:04Z")
i like CommandLine::OptionParser
([http://rubyforge.org/docman/view.php/632/170/index.html\](http://rubyforge.org/docman/view.php/632/170/index.html%5C))
because it's documentation is better than average as well
as its features.
it doesn't appear to be the ruby standard, however, but for
in-house projects there's a lot to like.
Eric J. Roode wrote:
> **···**
>
> > Greetings,
> >
> > I'm new to ruby (from Perl). I notice there are several command-line options parsing modules. The two that stuck out were GetoptLong and OptionsParser. GetoptLong suffers from being "the same old Getopt". OptionsParser claims to be "more advanced and more ruby-like", but has extremely poor documentation.
> >
> > Are these the best two modules out there? Is there an emerging "standard" module? (In Perl, Getopt::Long is by far the most commonly-used module).
> >
> > (I apologize if this is a FAQ; I read the FAQ and did a google scan of past articles. Most of what I found was authors announcing their own options-
> > parsing modules).
> >
> > Thanks in advance,
---
### Author:  [@mathew](https://rubytalk.org/u/mathew)
#### Post date: [28 December 2005 04:17 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/3 "2005-12-28T04:17:54Z")
Eric J. Roode wrote:
> GetoptLong suffers from being "the same old Getopt".
Well, what do you expect from an options parser? It's pretty much a solved problem, and using the standard getopt algorithms has the advantage that users know what to expect.
mathew
> **···**
>
> --
> \ My parents went to the lost kingdom of Hyrule
> and all I got was this lousy triforce.
---
### Author:  [@Robert](https://rubytalk.org/u/Robert)
#### Post date: [28 December 2005 13:37 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/4 "2005-12-28T13:37:54Z")
I used to use GetopLong in the beginning but switched to OptionParser. Agreee, the documentation could be better but if you look carefully at the example given in RDoc you get pretty much everything you need. I'm not sure about a standard parser but my impression was that OptionParser is more widely used. But I may be wrong here.
Kind regards
robert
> **···**
>
> Eric J. Roode \ wrote:
>
> > Greetings,
> >
> > I'm new to ruby (from Perl). I notice there are several
> > command-line options parsing modules. The two that stuck out were
> > GetoptLong and OptionsParser. GetoptLong suffers from being "the
> > same old Getopt". OptionsParser claims to be "more advanced and more
> > ruby-like", but has extremely poor documentation.
> >
> > Are these the best two modules out there? Is there an emerging
> > "standard" module? (In Perl, Getopt::Long is by far the most
> > commonly-used module).
---
### Author:  [@Jim\_Freeze2](https://rubytalk.org/u/Jim_Freeze2)
#### Post date: [28 December 2005 14:23 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/5 "2005-12-28T14:23:48Z")
Yikes.
That is old documenetation and the link on Rubyforge was to be replaced eons
ago. The new docs are at:
[http://rubyforge.org/docman/view.php/632/233/posted-docs.index.html](http://rubyforge.org/docman/view.php/632/233/posted-docs.index.html)
There you will find the option parser docs after Application section. For
the most part, if you use the CommandLine::Application class, you don't need
to get
your hands that dirty with CommandLine::OptionParser.
If you have any questions, just post a question or send me
a private email. I plan to post a video on the usage this week. Maybe a
rails like video will generate more interest. 🙂
> **···**
>
> On 12/27/05, Lou Vanek \ wrote:
>
> > i like CommandLine::OptionParser
> > ([http://rubyforge.org/docman/view.php/632/170/index.html\](http://rubyforge.org/docman/view.php/632/170/index.html%5C))
> > because it's documentation is better than average as well
> > as its features.
> > it doesn't appear to be the ruby standard, however, but for
> > in-house projects there's a lot to like.
>
> --
> Jim Freeze
---
### Author:  [@Steve\_Litt](https://rubytalk.org/u/Steve_Litt)
#### Post date: [28 December 2005 15:20 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/6 "2005-12-28T15:20:13Z")
Does OptionParser come with standard Ruby?
SteveT
Steve Litt
> **[Troubleshooters.Com](http://www.troubleshooters.com)**
>
> The process and mindset of troubleshooting.
slitt@troubleshooters.com
> **···**
>
> On Wednesday 28 December 2005 08:37 am, Robert Klemme wrote:
>
> > Eric J. Roode \ wrote:
> > \> Greetings,
> > \>
> > \> I'm new to ruby (from Perl). I notice there are several
> > \> command-line options parsing modules. The two that stuck out were
> > \> GetoptLong and OptionsParser. GetoptLong suffers from being "the
> > \> same old Getopt". OptionsParser claims to be "more advanced and more
> > \> ruby-like", but has extremely poor documentation.
> > \>
> > \> Are these the best two modules out there? Is there an emerging
> > \> "standard" module? (In Perl, Getopt::Long is by far the most
> > \> commonly-used module).
> >
> > I used to use GetopLong in the beginning but switched to OptionParser.
> > Agreee, the documentation could be better but if you look carefully at the
> > example given in RDoc you get pretty much everything you need. I'm not
> > sure about a standard parser but my impression was that OptionParser is
> > more widely used. But I may be wrong here.
> >
> > Kind regards
> >
> > robert
---
### Author:  [@Eric\_J\_Roode](https://rubytalk.org/u/Eric_J_Roode)
#### Post date: [28 December 2005 22:52 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/7 "2005-12-28T22:52:54Z")
mathew \ wrote in news:wjosf.9901$9e.8623
@tornado.texas.rr.com:
> Eric J. Roode wrote:
>
> > GetoptLong suffers from being "the same old Getopt".
>
> Well, what do you expect from an options parser? It's pretty much a
> solved problem, and using the standard getopt algorithms has the
> advantage that users know what to expect.
Well... that's not \*bad\*, but I guess I had expected something a bit more
ruby-like. Whatever that means. 🙂
> **···**
>
> --
> Eric
> `$=`;$\_=\%!;($\_)=/(.)/;$==++$|;($.,$/,$,$\,$",$;,$^,$#,$~,$\*,$:,@%)=(
> $!=~/(.)(.).(.)(.)(.)(.)..(.)(.)(.)..(.)......(.)/,$"),$=++;$.++;$.++;
> $\_++;$\_++;($\_,$\,$,)=($~.$"."$;$/$%[$?]$\_$\$,$:$%[$?]",$"&$~,$#,);$,++
> ;$,++;$^|=$";`$_$\$,$/$:$;$~$*$%[$?]$.$~$*${#}$%[$?]$;$\$"$^$~$*.\>&$=`
---
### Author:  [@Eric\_J\_Roode](https://rubytalk.org/u/Eric_J_Roode)
#### Post date: [28 December 2005 23:04 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/8 "2005-12-28T23:04:26Z")
"Robert Klemme" \ wrote in
news:41fiouF1e6diiU1@individual.net:
> I used to use GetopLong in the beginning but switched to OptionParser.
> Agreee, the documentation could be better but if you look carefully at
> the example given in RDoc you get pretty much everything you need.
> I'm not sure about a standard parser but my impression was that
> OptionParser is more widely used. But I may be wrong here.
I disagree about the example being all you need.
Here's the first option in the example:
# Mandatory argument.
opts.on("-r", "--require LIBRARY",
"Require the LIBRARY before executing your script") do |lib|
options.library \<\< lib
end
I am new to ruby, so I don't know what "options.library \<\< lib" means. I
thought that that introduced a here-doc string.
The second example:
# Optional argument; multi-line description.
opts.on("-i", "--inplace [EXTENSION]",
"Edit ARGV files in place",
" (make backup if EXTENSION supplied)") do |ext|
...
It took me a lot of staring at the code before it dawned on me that it
was the \*brackets\* that made it an optional argument.
The final example:
# Another typical switch to print the version.
opts.on\_tail("--version", "Show version") do
puts OptionParser::Version.join('.')
exit
end
I can't figure out how the on\_tail method differs from the on method or
the on\_head method. Reading the source isn't helping. The example
sucks.
The previous example has this comment:
# No argument, shows at tail. This will print an options summary.
"Shows at tail"??
At the end of the parse() method (and why is it self.parse, not just
parse?), there is this:
opts.parse!(args)
I can't tell what function that performs for the class.
I can't tell how to make an option mandatory, how to configure it so that
some options require certain others or conflict with certain others.
It looks like a fine, powerful module. But its lack of documentation
makes it pretty much useless for anyone who doesn't already know how to
use it.
I come from the Perl world. You simply do not release a module to Perl's
CPAN unless it is thoroughly documented. The vast majority of CPAN
modules have quite good documentation -- or at least, thorough
documentation. I'm quite surprised to find that the situation is so
different in the ruby world.
> **···**
>
> --
> Eric
> `$=`;$\_=\%!;($\_)=/(.)/;$==++$|;($.,$/,$,$\,$",$;,$^,$#,$~,$\*,$:,@%)=(
> $!=~/(.)(.).(.)(.)(.)(.)..(.)(.)(.)..(.)......(.)/,$"),$=++;$.++;$.++;
> $\_++;$\_++;($\_,$\,$,)=($~.$"."$;$/$%[$?]$\_$\$,$:$%[$?]",$"&$~,$#,);$,++
> ;$,++;$^|=$";`$_$\$,$/$:$;$~$*$%[$?]$.$~$*${#}$%[$?]$;$\$"$^$~$*.\>&$=`
---
### Author:  [@Robert](https://rubytalk.org/u/Robert)
#### Post date: [28 December 2005 16:52 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/9 "2005-12-28T16:52:53Z")
Will there be stunt scenes with options and a high speed car chase?
robert
> **···**
>
> Jim Freeze \ wrote:
>
> > If you have any questions, just post a question or send me
> > a private email. I plan to post a video on the usage this week. Maybe
> > a rails like video will generate more interest. 🙂
---
### Author:  [@Jim\_Freeze2](https://rubytalk.org/u/Jim_Freeze2)
#### Post date: [29 December 2005 00:30 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/10 "2005-12-29T00:30:48Z")
Hi Eric
You may want to give CommandLine a try.
From the examples you give, this is how I would write an app:
require 'rubygems'
require 'commandline'
class MyApp \< CommandLine::Application
def initialize
# Mandatory argument
option :names =\> %w(--require -r),
:opt\_description =\> "Require the LIBRARY "+
"before executing your script",
:arg\_description =\> "LIBRARY",
:opt\_found =\> get\_arg,
:opt\_not\_found =\> required
option :names =\> %w(--inplace -i),
:arity =\> [0,1],
:opt\_description =\> "Edit ARGV files in place",
:arg\_description =\> "[EXTENSION]",
:opt\_found =\> get\_arg,
end
def main
#put your code here
p opts
end
end#class MyApp
I don't know what #on\_tail does either.
> **···**
>
> --
> Jim Freeze
---
### Author:  [@GS1](https://rubytalk.org/u/GS1)
#### Post date: [29 December 2005 05:37 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/11 "2005-12-29T05:37:54Z")
Eric J. Roode wrote:
> mathew \ wrote in news:wjosf.9901$9e.8623
> @tornado.texas.rr.com:
>
> \> Eric J. Roode wrote:
> \>\> GetoptLong suffers from being "the same old Getopt".
> \>
> \> Well, what do you expect from an options parser? It's pretty much a
> \> solved problem, and using the standard getopt algorithms has the
> \> advantage that users know what to expect.
>
> Well... that's not \*bad\*, but I guess I had expected something a bit more
> ruby-like. Whatever that means. 🙂
That's a good expectation to have.
You mention OptionParser has poor documentation. While it's not
complete, I find the example at [1] is quite adequate.
[1]
[http://ruby-doc.org/stdlib/libdoc/optparse/rdoc/classes/OptionParser.html](http://ruby-doc.org/stdlib/libdoc/optparse/rdoc/classes/OptionParser.html)
Gavin
---
### Author:  [@GS1](https://rubytalk.org/u/GS1)
#### Post date: [29 December 2005 05:47 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/12 "2005-12-29T05:47:54Z")
Eric J. Roode wrote:
> I disagree about the example being all you need.
Please disregard my other reply in this thread. Your points are
perfectly valid and I'll try to improve the documentation.
> Here's the first option in the example:
>
> # Mandatory argument.
> opts.on("-r", "--require LIBRARY",
> "Require the LIBRARY before executing your script") do |lib|
> options.library \<\< lib
> end
>
> I am new to ruby, so I don't know what "options.library \<\< lib" means. I
> thought that that introduced a here-doc string.
The documentation's not at fault here: knowledge of Ruby is assumed 🙂
> The second example:
>
> # Optional argument; multi-line description.
> opts.on("-i", "--inplace [EXTENSION]",
> "Edit ARGV files in place",
> " (make backup if EXTENSION supplied)") do |ext|
> ...
>
> It took me a lot of staring at the code before it dawned on me that it
> was the \*brackets\* that made it an optional argument.
That will be easy to point out in the docs. Thanks.
> The final example:
>
> # Another typical switch to print the version.
> opts.on\_tail("--version", "Show version") do
> puts OptionParser::Version.join('.')
> exit
> end
>
> I can't figure out how the on\_tail method differs from the on method or
> the on\_head method. Reading the source isn't helping. The example
> sucks.
It means to show the "--version" option at the end (the "tail") of the
options list.
> At the end of the parse() method (and why is it self.parse, not just
> parse?), there is this:
>
> opts.parse!(args)
>
> I can't tell what function that performs for the class.
Hopefully I can clear this up. The difference between parse and parse!
is that parse! swallows ARGV.
> I can't tell how to make an option mandatory, how to configure it so that
> some options require certain others or conflict with certain others.
A "mandatory option" is a contradiction 🙂 You need to test for the
presence of an option in your own code.
> I come from the Perl world. You simply do not release a module to Perl's
> CPAN unless it is thoroughly documented. The vast majority of CPAN
> modules have quite good documentation -- or at least, thorough
> documentation. I'm quite surprised to find that the situation is so
> different in the ruby world.
While not disagreeing in the least, I bet there are plenty of
badly-documented Perl modules, but they're not the often-used ones, so
they don't detract from the "Perl modules are well documented" meme.
Ruby is certainly worse, though!
Gavin
---
### Author:  [@Robert](https://rubytalk.org/u/Robert)
#### Post date: [29 December 2005 10:47 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/13 "2005-12-29T10:47:54Z")
It seems to me that your posting pretty much confirms what I said: I didn't claim it's "all you need" but that it gets you pretty far, if you "look carefully". 🙂 Admittedly it's not so easy for someone new to Ruby...
Kind regards
robert
> **···**
>
> Eric J. Roode \ wrote:
>
> > "Robert Klemme" \ wrote in
> > news:41fiouF1e6diiU1@individual.net:
> >
> > > I used to use GetopLong in the beginning but switched to
> > > OptionParser. Agreee, the documentation could be better but if you
> > > look carefully at the example given in RDoc you get pretty much
> > > everything you need. I'm not sure about a standard parser but my
> > > impression was that OptionParser is more widely used. But I may be
> > > wrong here.
> >
> > I disagree about the example being all you need.
---
### Author:  [@Jim\_Freeze2](https://rubytalk.org/u/Jim_Freeze2)
#### Post date: [28 December 2005 17:09 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/14 "2005-12-28T17:09:09Z")
It will be action packed. There will be trains, rubies
and high speed typing! 😉
> **···**
>
> On 12/28/05, Robert Klemme \ wrote:
>
> > Will there be stunt scenes with options and a high speed car chase?
>
> --
> Jim Freeze
---
### Author:  [@Daniel\_Berger2](https://rubytalk.org/u/Daniel_Berger2)
#### Post date: [29 December 2005 07:42 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/15 "2005-12-29T07:42:54Z")
Gavin Sinclair wrote:
\
> While not disagreeing in the least, I bet there are plenty of
> badly-documented Perl modules, but they're not the often-used ones, so
> they don't detract from the "Perl modules are well documented" meme.
>
> Ruby is certainly worse, though!
>
> Gavin
How's that shell documentation coming along?
Dan
---
### Author:  [@Rover\_Rhubarb](https://rubytalk.org/u/Rover_Rhubarb)
#### Post date: [3 May 2007 11:54 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/16 "2007-05-03T11:54:48Z")
> A "mandatory option" is a contradiction 🙂 You need to test for the
> presence of an option in your own code.
This is a fair point, but for complex command lines we sometimes really
need options that are not optional. For example, I'm working on a ruby
xmltv-like scraper, that has a bunch of regular options, plus essential
arguments like --config CONFIG\_FILE and --scraper SCRAPER\_FILE for
specifying files that are necessary.
I want to use options for these rather than arguments because they are
both files and I prefer that the user specify the option --config or
--scraper rather than having to get the order of them right on the
command line.
So you see, I need an "option" that is mandatory in addition to it
having a mandatory argument.
Sure I could do it in my own code - but given this is a common case I'm
tempted to extend OptionParser to do it so that I can get at the option
description when I report that its missing you see? This is why it
should probably be a feature of OptionParser - to tie the error message
to the switch that's missing. I don't think I can be bothered wading
into that code myself, so I guess I'll do something a little hackier -
test my options and repeat the option descriptions.
But how about it Gavin?
Also - even if you don't - you should probably clearly document the
fact this isn't available. The frequent use of "MANDATORY" in the
example led me and probably many others to think it was bug that my
mandatory arguments weren't reported as missing. It took me a while to
realize that the word "argument" was key here. It also took me a while
to realize that the square brackets were important.
> **···**
>
> --
> Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).
---
### Author:  [@GS1](https://rubytalk.org/u/GS1)
#### Post date: [29 December 2005 12:07 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/17 "2005-12-29T12:07:54Z")
Daniel Berger wrote:
> How's that shell documentation coming along?
Not too well, just yet!
Gavin
---
### Author:  [@Felipe\_Contreras](https://rubytalk.org/u/Felipe_Contreras)
#### Post date: [3 May 2007 12:12 UTC](https://rubytalk.org/t/command-line-option-parsing/23639/18 "2007-05-03T12:12:36Z")
I agree completely.
The wording should be: mandatory option argument, not option.
And yes, it makes sense to /also/ make some options mandatory.
> **···**
>
> On 5/3/07, Rover Rhubarb \ wrote:
>
> > \> A "mandatory option" is a contradiction 🙂 You need to test for the
> > \> presence of an option in your own code.
> >
> > This is a fair point, but for complex command lines we sometimes really
> > need options that are not optional. For example, I'm working on a ruby
> > xmltv-like scraper, that has a bunch of regular options, plus essential
> > arguments like --config CONFIG\_FILE and --scraper SCRAPER\_FILE for
> > specifying files that are necessary.
> >
> > I want to use options for these rather than arguments because they are
> > both files and I prefer that the user specify the option --config or
> > --scraper rather than having to get the order of them right on the
> > command line.
> >
> > So you see, I need an "option" that is mandatory in addition to it
> > having a mandatory argument.
> >
> > Sure I could do it in my own code - but given this is a common case I'm
> > tempted to extend OptionParser to do it so that I can get at the option
> > description when I report that its missing you see? This is why it
> > should probably be a feature of OptionParser - to tie the error message
> > to the switch that's missing. I don't think I can be bothered wading
> > into that code myself, so I guess I'll do something a little hackier -
> > test my options and repeat the option descriptions.
> >
> > But how about it Gavin?
> >
> > Also - even if you don't - you should probably clearly document the
> > fact this isn't available. The frequent use of "MANDATORY" in the
> > example led me and probably many others to think it was bug that my
> > mandatory arguments weren't reported as missing. It took me a while to
> > realize that the word "argument" was key here. It also took me a while
> > to realize that the square brackets were important.
>
> --
> Felipe Contreras