Hello!
I'm really enjoying ruby; the gem framework is absolutely amazing.
When I was trying to use multiple versions of Ruby on the same system,
I ran across this one confusing aspect: the executables for gems
didn't have the same naming convention as the "ruby" and "irb"
executables.
So I filed bug 1728[1] and Eric Hodel was kind enough to point me to
this mailing list.
It seems that "gem --format-executable" should default to "true"
because the binaries created have the name of the "ruby" executable
embedded in them (in the #! at the top).
Here are two use cases to help illustrate:
----use case 1-----------------------
I install ruby 1.8.
I use "./configure" when compiling it.
The binaries are in /usr/bin/ and do not have a suffix.
I decide I want to work on ruby 1.9.1 as well.
I use "./configure --program-suffix=19" when compiling it.
The binaries are also in /usr/bin but all end with "19", such as "/usr/
bin/ruby19".
Lets say I ZenTest for 1.8:
$ gem install ZenTest
This creates /usr/bin/autotest. This executable is intimately tied to
ruby 1.8; it begins with "#!/usr/bin/ruby -ws" -- it cannot be used
for ruby 1.9 (yet) because the libraries are not installed in ruby 1.9
and the executable it points to is the 1.8 executable.
Now lets say I want to install autotest for ruby 1.9:
$ gem19 install ZenTest
By default, no new binaries are created since they already exists.
The executable /usr/bin/autotest is *still* tied to ruby 1.8.
This causes confusion by the user; they just installed autotest for
ruby 1.9 but it still is running ruby 1.8.
-----------------------------------
----use case 2-----------------------
My system administrator installs ruby 1.8 using "./configure" with no
arguments.
My system administrator installs ruby 1.9.1 using "./configure --
program-suffix=19"
I (a non-system-administrator) wants to install ZenTest for both:
$ gem install ZenTest
[output showing it is installed to ~/.gem]
$ gem19 install ZenTest
[output showing it is installed to ~/.gem]
So now I have two "autotest" binaries:
~/.gem/ruby/1.8/bin/autotest
and
~/.gem/ruby/1.9.1/bin/autotest
If my PATH includes both, then which "autotest" I get depends on my
PATH order. The only way I can distinguish between the two
executables is by changing my PATH on the fly. Not very useful if I
want to be able to easily switch between both versions to verify it
works in both versions of Ruby.
-----------------------------------
As you can see it can be rather confusing for "--format-executable"
not to be the default.
It was doubly confusing for me because everything else worked so
well. :-)
Ciao!
[1] http://redmine.ruby-lang.org/issues/show/1728
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