# Main-0.0.1 - command line apps for the truly lazy **URL:** \ **Category:** Ruby\ **Created:** [March 20, 2007, 7:31pm UTC](https://www.ruby-forum.com/t/main-0-0-1-command-line-apps-for-the-truly-lazy/89474 "2007-03-20T19:31:25Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 20, 2007, 7:31pm UTC](https://www.ruby-forum.com/t/main-0-0-1-command-line-apps-for-the-truly-lazy/89474/1 "2007-03-20T19:31:25Z")
NAME main.rb SYNOPSIS a class factory and dsl for generating real main programs real quick URI [http://rubyforge.org/projects/codeforpeople/](http://rubyforge.org/projects/codeforpeople/) [http://codeforpeople.com/lib/ruby/](http://codeforpeople.com/lib/ruby/) INSTALL $sudo gem install main DESCRIPTION main.rb is a library which simplifies and unifies the details of creating command line programs. for instance, this program ``` require 'main' Main { argument 'foo' option 'bar' def run p params['foo'] p params['bar'] exit_success! end } ``` sets up a program which requires one argument, ‘bar’, and which may accept one command line switch, ‘–foo’ in addition to the single option which is always accepted and handled appropriately: ‘–help’, ‘-h’. for simple programs this is a real time saver but it’s for more complex applications where main.rb’s unification of parameter parsing, class configuration dsl, and auto-generation of usage messages can really streamline command line application development. for example the following ‘a.rb’ program: ``` require 'main' Main { argument('foo'){ cast :int } keyword('bar'){ arity 2 cast :float defaults 0.0, 1.0 } option('foobar'){ argument :optional description 'the foobar option is very handy' } environment('BARFOO'){ cast :list_of_bool synopsis 'export barfoo=value' } def run p params['foo'].value p params['bar'].values p params['foobar'].value p params['BARFOO'].value end } ``` when run with a command line of ``` BARFOO=true,false,false ruby a.rb 42 bar=40 bar=2 --foobar=a ``` will produce ``` 42 [40.0, 2.0] "a" [true, false, false] ``` while a command line of ``` ruby a.rb --help ``` will produce ``` NAME a.rb SYNOPSIS a.rb foo [bar=bar] [options]+ PARAMETERS * foo [1 -> int(foo)] * bar=bar [2 ~> float(bar=0.0,1.0)] * --foobar=[foobar] [1 ~> foobar] the foobar option is very handy * --help, -h * export barfoo=value ``` and this shows how all of argument, keyword, option, and environment parsing can be declartively dealt with in a unified fashion - the dsl for all parameter types is the same - and how auto synopsis and usage generation saves keystrokes. the parameter synopsis is compact and can be read as ``` * foo [1 -> int(foo)] 'one argument will get processed via int(argument_name)' 1 : one argument -> : will get processed (the argument is required) int(foo) : the cast is int, the arg name is foo * bar=bar [2 ~> float(bar=0.0,1.0)] 'two keyword arguments might be processed via ``` float(bar=0.0,1.0)’ ``` 2 : two arguments ~> : might be processed (the argument is ``` optional) float(bar=0.0,1.0) : the cast will be float, the default values are 0.0 and 1.0 ``` * --foobar=[foobar] [1 ~> foobar] 'one option with optional argument may be given directly' * --help, -h no synopsis, simple switch takes no args and is not required * export barfoo=value a user defined synopsis ``` SAMPLES \<========\< samples/a.rb \>========\> ~ \> cat samples/a.rb ``` require 'main' ARGV.replace %w( 42 ) if ARGV.empty? Main { argument('foo'){ required # this is the default cast :int # value cast to Fixnum validate{|foo| foo == 42} # raises error in failure case description 'the foo param' # shown in --help } def run p params['foo'].given? p params['foo'].value end } ``` ~ \> ruby samples/a.rb ``` true 42 ``` ~ \> ruby samples/a.rb --help ``` NAME a.rb SYNOPSIS a.rb foo [options]+ PARAMETERS * foo [1 -> int(foo)] the foo param * --help, -h ``` \<========\< samples/b.rb \>========\> ~ \> cat samples/b.rb ``` require 'main' ARGV.replace %w( 40 1 1 ) if ARGV.empty? Main { argument('foo'){ arity 3 # foo will given three ``` times cast :int # value cast to Fixnum validate{|foo| [40,1].include? foo} # raises error in failure case description ‘the foo param’ # shown in --help } ``` def run p params['foo'].given? p params['foo'].values end } ``` ~ \> ruby samples/b.rb ``` true [40, 1, 1] ``` ~ \> ruby samples/b.rb --help ``` NAME b.rb SYNOPSIS b.rb foo [options]+ PARAMETERS * foo [3 -> int(foo)] the foo param * --help, -h ``` \<========\< samples/c.rb \>========\> ~ \> cat samples/c.rb ``` require 'main' ARGV.replace %w( foo=40 foo=2 bar=false ) if ARGV.empty? Main { keyword('foo'){ required # by default keywords are not required arity 2 cast :float } keyword('bar'){ cast :bool } def run p params['foo'].given? p params['foo'].values p params['bar'].given? p params['bar'].value end } ``` ~ \> ruby samples/c.rb ``` true [40.0, 2.0] true false ``` ~ \> ruby samples/c.rb --help ``` NAME c.rb SYNOPSIS c.rb foo=foo [bar=bar] [options]+ PARAMETERS * foo=foo [2 -> float(foo)] * bar=bar [1 ~> bool(bar)] * --help, -h ``` \<========\< samples/d.rb \>========\> ~ \> cat samples/d.rb ``` require 'main' ARGV.replace %w( --foo=40 -f2 ) if ARGV.empty? Main { option('foo', 'f'){ required # by default options are not required, we could use ``` ‘foo=foo’ # above as a shortcut argument\_required arity 2 cast :float } ``` option('bar=[bar]', 'b'){ # note shortcut syntax for optional ``` args # argument\_optional # we could also use this method cast :bool default false } ``` def run p params['foo'].given? p params['foo'].values p params['bar'].given? p params['bar'].value end } ``` ~ \> ruby samples/d.rb ``` true [40.0, 2.0] true false ``` ~ \> ruby samples/d.rb --help ``` NAME d.rb SYNOPSIS d.rb --foo=foo [options]+ PARAMETERS * --foo=foo, -f [2 -> float(foo)] * --bar=[bar], -b [1 ~> bool(bar=false)] * --help, -h ``` DOCS test/main.rb find lib|xargs -n1 vi -R HISTORY 0.0.1 ``` initial version. this version extracts much of the functionality ``` of alib’s (gen install alib) Alib.script main program generator and also some of jim’s freeze’s excellent CommandLine::Aplication into what i hope is a simpler and more unified interface -a ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 20, 2007, 8:38pm UTC](https://www.ruby-forum.com/t/main-0-0-1-command-line-apps-for-the-truly-lazy/89474/2 "2007-03-20T20:38:34Z")
On 3/20/07, Ara.T.Howard [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > NAME > main.rb > > SYNOPSIS > a class factory and dsl for generating real main programs real quick Excellent looking library. I have some fascination with writing CLI apps, and have used the commandline gem extensively. My one complaint with that library was the obscure syntax used for parsing command line options. Can the options parsed be used outside the Main { } declaration? For small scripts, the “run” method is fine, but for larger apps it becomes necessary to break things up. Specifically, I am thinking of some highline driven apps I have which would benefit from the option parsing provided here. Justin ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 20, 2007, 8:57pm UTC](https://www.ruby-forum.com/t/main-0-0-1-command-line-apps-for-the-truly-lazy/89474/3 "2007-03-20T20:57:36Z")
On Wed, 21 Mar 2007, Justin B. wrote: > Excellent looking library. I have some fascination with writing CLI apps, > and have used the commandline gem extensively. My one complaint with that > library was the obscure syntax used for parsing command line options. > > Can the options parsed be used outside the Main { } declaration? For small > scripts, the “run” method is fine, but for larger apps it becomes necessary > to break things up. Specifically, I am thinking of some highline driven apps > I have which would benefit from the option parsing provided here. harp:~ \> cat a.rb require ‘rubygems’ require ‘main’ ARGV.replace %w( --foo=42 42.0 ) main = Main.new{ option(‘foo=’){ cast :int } option(‘bar=’){ cast :float } } p main.param[‘foo’] p main.param[‘bar’] harp:~ \> ruby a.rb #\ #\ i realize, as i post this, that i’d meant for one to be able to say argv = %w( --foo=42 42.0 ) env = {‘PATH’ =\> ‘/usr/loca/bin’} main = Main.new(argv, env){ option(‘foo=’){ cast :int } option(‘bar=’){ cast :float } } but neglected to pass some information through. i’ll think about it and ensure that’s possible v.s directly manipulating ARGV this is quite a re-work of what’s in alib, so i’m all ears for comments/feature-requests. btw. the usage can be overridden simply with Main{ usage ‘my usage string’ } regards. -a ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 21, 2007, 8:21pm UTC](https://www.ruby-forum.com/t/main-0-0-1-command-line-apps-for-the-truly-lazy/89474/4 "2007-03-21T20:21:26Z")
On Thu, 22 Mar 2007, Jason R. wrote: > Could you make the main gem dependent on other gems? I had to manually > install attributes and arrayfields to get main to run. Otherwise, this is a > cool little library, thanks! will do. it was an oversight. i’m making a few mods today and should release later in the aftertoon. cheers. -a ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [March 21, 2007, 7:43pm UTC](https://www.ruby-forum.com/t/main-0-0-1-command-line-apps-for-the-truly-lazy/89474/5 "2007-03-21T19:43:13Z")
Could you make the main gem dependent on other gems? I had to manually install attributes and arrayfields to get main to run. Otherwise, this is a cool little library, thanks! Jason