getting rid of $0

[Michel Demazure]

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 <nice name to be found> then...

 

[Tim Pease]

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 <nice name to be found> then...

require 'English'

if __FILE__ == $PROGRAM_NAME
...
end


Blessings,
TwP

 

[Alex Young]

require 'English'

if __FILE__ == $PROGRAM_NAME
...
end

Does that solve the problem? Isn't that vulnerable to the same issues
as just using $0?

 

[Tim Pease]

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

 

[Ryan Davis]

Does that solve the problem? Isn't that vulnerable to the same
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.

 

[Jano Svitok]

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 <nice name to be found> 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

 

[ara.t.howard]

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