Difference between $0 and __FILE__

Ruby
1

i have a script in my HOME/bin :

/Users/yt/bin/path_test.rb

my “HOME/bin” is in the PATH

then, if from this script, i outputs $0 and FILE

with :

path_test.rb i got :
$0 = /Users/yt/bin/path_test.rb
FILE = /Users/yt/bin/path_test.rb

and the same outputs with :
/Users/yt/bin/path_test.rb

why do i have the same outputs in this case ?

in fact i’m looking that because i do have Ruby class extension in a
subfolder of “HOME/bin”, namely :
HOME/bin/ruby_ext
where i put my extension for classes of which i could require :
require “#{File.dirname($0)}/ruby_ext/ansi_color”

what’s the best way to require in that case, does i need an "absolute
path (starting from / ) or not ?

2

On 15.05.2010 10:33, Une Bévue wrote:

path_test.rb i got :
$0 = /Users/yt/bin/path_test.rb
FILE = /Users/yt/bin/path_test.rb

and the same outputs with :
/Users/yt/bin/path_test.rb

why do i have the same outputs in this case ?

Because the shell will also expand full names. How does your PATH look
like? I assume you set something like PATH="${PATH}:${HOME}/bin" - in
that case you’ll have the absolute path to ~/bin in your PATH and
consequently the script is invoked with absolute path.

in fact i’m looking that because i do have Ruby class extension in a
subfolder of “HOME/bin”, namely :
HOME/bin/ruby_ext
where i put my extension for classes of which i could require :
require “#{File.dirname($0)}/ruby_ext/ansi_color”

what’s the best way to require in that case, does i need an "absolute
path (starting from / ) or not ?

IMHO the best way is to define a local location of library files and set
RUBYLIB to that directory (I use “$HOME/lib/ruby” for that because I
prefer to have lib code separate from programs, but in your case you
could also use “$HOME/bin”).

If you want to do it on a per script basis you could do this at the
beginning of your script (i.e. before any requires):

$:.unshift “/your/folder/here”

Kind regards

robert

3

2010/5/15 Une Bévue [email protected]

in fact i’m looking that because i do have Ruby class extension in a
bénéfique à l’âme du poète blême, ainsi qu’à son cÅ“ur & cætera ! »
(© Jean-Paul Blanc)

Having a hard time understanding your question. Here are some possible
thoughts:

Difference between $0 and FILE
$ echo ‘p $0 , FILE’ > callee0.rb
$ echo ‘p $0 , FILE’ > callee1.rb
$ echo ‘p $0 , FILE’ > callee2.rb
$ echo ‘3.times { |i| require “callee#{i}” ; puts }’ > main_prog.rb
$ ruby main_prog.rb
“main_prog.rb”
“./callee0.rb”

“main_prog.rb”
“./callee1.rb”

“main_prog.rb”
“./callee2.rb”

You have the same output because
The program that was run is the same as the file being checked

How to require relative files:
class File - RDoc Documentation
Tip: Relative paths with File.expand_path - Tom Ward's Blog
In this case, that probably means you want
File.expand_path(‘ruby_ext/ansi_color’,FILE)

4

Robert K. [email protected] wrote:

require “#{File.dirname($0)}/ruby_ext/ansi_color”

what’s the best way to require in that case, does i need an "absolute
path (starting from / ) or not ?

OK, i see.

IMHO the best way is to define a local location of library files and set
RUBYLIB to that directory (I use “$HOME/lib/ruby” for that because I
prefer to have lib code separate from programs, but in your case you
could also use “$HOME/bin”).

If you want to do it on a per script basis you could do this at the
beginning of your script (i.e. before any requires):

$:.unshift “/your/folder/here”

fine thanks !