# Getting rid of $0 **URL:** \ **Category:** Ruby\ **Created:** [July 2, 2007, 7:59pm UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363 "2007-07-02T19:59:42Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![micheldogger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b5e925/32.png) [@micheldogger](https://www.ruby-forum.com/u/micheldogger)\ **Post date:** [July 2, 2007, 7:59pm UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363/1 "2007-07-02T19:59:42Z")
The common idiom if **FILE** == $0 then … gives bugs when $0 is not what one would expect, for instance under a debugger, or in rubyscript2exe, etc. There should be a primitive test if then… ---
**Author:** ![micheldogger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b5e925/32.png) [@micheldogger](https://www.ruby-forum.com/u/micheldogger)\ **Post date:** [July 2, 2007, 8:10pm UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363/2 "2007-07-02T20:10:49Z")
On 7/2/07, Michel D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > The common idiom > if **FILE** == $0 then … > gives bugs when $0 is not what one would expect, for instance under a > debugger, or in rubyscript2exe, etc. > > There should be a primitive test > if then… require ‘English’ if **FILE** == $PROGRAM\_NAME … end Blessings, TwP ---
**Author:** ![micheldogger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b5e925/32.png) [@micheldogger](https://www.ruby-forum.com/u/micheldogger)\ **Post date:** [July 2, 2007, 8:12pm UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363/3 "2007-07-02T20:12:50Z")
Tim P. wrote: > require ‘English’ > > if **FILE** == $PROGRAM\_NAME > … > end Does that solve the problem? Isn’t that vulnerable to the same issues as just using $0? ---
**Author:** ![micheldogger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b5e925/32.png) [@micheldogger](https://www.ruby-forum.com/u/micheldogger)\ **Post date:** [July 2, 2007, 8:22pm UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363/4 "2007-07-02T20:22:51Z")
On 7/2/07, Alex Y. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > require ‘English’ > > > > if **FILE** == $PROGRAM\_NAME > > … > > end > > Does that solve the problem? Isn’t that vulnerable to the same issues > as just using $0? You’re correct! That does not solve the problem. 😕 Hmmm … the solution I use most often is to have a top-level function that runs the application. This top-level function is called by a separate Ruby script. class MyApp def self.run( args ) new(args).run end … end And in an executable file called “my\_app” #!/usr/bin/env ruby require ‘MyApp’ MyApp.run ARGV I try to avoid the **FILE** == $0 idiom when I distribute code. You run into the problems the original poster pointed out, and rubygems also wrappers up all your executables with it’s own special calling semantics (provides compatibility between windows / \*nix). Not the answer you want to hear, but, “don’t do that”. Sorry 😕 TwP ---
**Author:** ![micheldogger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b5e925/32.png) [@micheldogger](https://www.ruby-forum.com/u/micheldogger)\ **Post date:** [July 2, 2007, 11:04pm UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363/5 "2007-07-02T23:04:16Z")
On 7/2/07, Michel D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > The common idiom > if **FILE** == $0 then … > gives bugs when $0 is not what one would expect, for instance under a > debugger, or in rubyscript2exe, etc. > > There should be a primitive test > if then… rcov provides for this case a special switch --replace-progname that does what the name says. Unfortunately, sometimes there’s still a mismatch between those two: one is ./something.rb while the other is just something.rb. Therefore I use the following variation of the idiom (I haven’t checked this under debugger or any other prog): if File.expand\_path( **FILE** )==File.expand\_path($0) I have posted a patch for ruby-prof that adds a similar switch and it has been accepted. Anyway, $0 seems to be a normal variable that you can set to anything you want, so creating a small wrapper script should not be a problem. E.g. $0 = ARGV.shift require $0 ---
**Author:** ![micheldogger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b5e925/32.png) [@micheldogger](https://www.ruby-forum.com/u/micheldogger)\ **Post date:** [July 2, 2007, 10:48pm UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363/6 "2007-07-02T22:48:13Z")
On Jul 2, 2007, at 11:11 , Alex Y. wrote: > issues as just using $0? > Solve what problem? The code is doing what you asked it to do, that > isn’t a problem, that’s programming. The code clearly reads “if this file is the program” which is NOT the case when run under a debugger. I’m not sure what rubyscript2exe generates, but my guess is that can be solved on their end somehow. I generally don’t want that code to run when I’m poking around in a debugger or something similar. If I do, I set the values inside the debugger and don’t worry about it. ---
**Author:** ![micheldogger](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b5e925/32.png) [@micheldogger](https://www.ruby-forum.com/u/micheldogger)\ **Post date:** [July 3, 2007, 8:44am UTC](https://www.ruby-forum.com/t/getting-rid-of-0/108363/7 "2007-07-03T08:44:17Z")
On Jul 2, 2007, at 3:03 PM, Jano S. wrote: > Anyway, $0 seems to be a normal variable that you can set to anything > you want, so creating a small wrapper script should not be a problem. > E.g. > > $0 = ARGV.shift > require $0 be careful, $0 is not a normal variable: cfp:~ \> cat a.rb $0 = ‘foobar’ puts `ps wwwaux|grep foobar` cfp:~ \> ruby a.rb ahoward 10371 2.6 -0.1 29204 1388 p2 S+ 12:41AM 0:00.01 foobar ahoward 10372 1.4 -0.0 27728 584 p2 S+ 12:41AM 0:00.00 sh -c ps wwwaux|grep foobar ahoward 10374 1.2 -0.0 27368 448 p2 S+ 12:41AM 0:00.00 grep foobar it actually assigns to c’s argv -a