Forum: Ruby Working directory for external commands

Hello everyone, I've been searching on google for a while now but I
can't find any solution to my question. Basically I want to be able to
specify the working directory for any external command I might launch,
without using ugly globals :S
What I'm trying to write is a wrapper class for git. As a client, I want
to be able to write, for example:

[code]
git = GitWrapper.new
puts git.status
[/code]

and of course I don't want to know what's happening inside status().

In order to invoke git I'm doing `git status`, or `"c:/program
files/git/bin/sh.exe" -c "git status"`, depending on the OS and other
things. The problem is, backticks as well as %x, system and friends rely
on Dir.pwd, so in order to get a valid result from git I should do:
[code]
def status()
    Dir.chdir("some/dir") do
        return `git status`
    end
end
[/code]
which I'd rather avoid for its obvious fragility:
[code]
git = GitWrapper.new
a = Thread.new {10000.times do {Dir.chdir("some/other/dir");
do_some_work(); `rm -rf '*'`}}
puts git.status() # OMG!!!!!111
a.join
[/code]

Any suggestions?

Duckz King_duckz wrote:
> Hello everyone, I've been searching on google for a while now but I
> can't find any solution to my question. Basically I want to be able to
> specify the working directory for any external command I might launch,
> without using ugly globals :S
> What I'm trying to write is a wrapper class for git. 

This doesn't directly answer your question, but have you looked at Grit?

Best,
-- 
Marnen Laibow-Koser
http://www.marnen.org
marnen@marnen.org

2010/2/9 Duckz King_duckz <king_duckz@yahoo.it>:
> [/code]
>        return `git status`
> [/code]
>
> Any suggestions?

The only safe way I can think of is to defer the chdir to a child
process.  The shortest form would be

irb(main):006:0> s=`cd /tmp && exec pwd`
=> "/tmp\n"
irb(main):007:0>

(Using "git status" instead of "pwd" of course.)

A Ruby solution would probably include IO.popen or popen3 and fork.

Kind regards

robert

@Marnen Laibow-Koser:
I didn't hear of it, but from a quick look it seems to allow a much 
cleaner solution, I'll look into that! Anyways, the global Dir problem 
has already occurred to me in other situations, and I'm still interested 
in finding a safe solution! I wonder why popen or system don't allow an 
optional parameter to specify the working directory!

@Robert Klemme:
Thanks for the hint, I guess I'll follow that path to write an intial 
version, before looking in depth into Grit. Are there any issues with 
fork implementation on Windows in Ruby 1.9.1? Still, I find it a shame 
you can't specify the cwd as a parameter (as in CreateProcess() on 
Windows for example, but I'm sure most OS have an equivalent).

Duckz King_duckz wrote:
> I guess I'll follow that path to write an intial 
> version, before looking in depth into Grit.

BTW, there are two gems: 'grit' and 'git'. I don't know what's the 
difference between them.

Albert Schlef wrote:
> Duckz King_duckz wrote:
>> I guess I'll follow that path to write an intial 
>> version, before looking in depth into Grit.
> 
> BTW, there are two gems: 'grit' and 'git'. I don't know what's the 
> difference between them.

Grit is pure Ruby.  I think the git gem is just a wrapper.

Best,
-- 
Marnen Laibow-Koser
http://www.marnen.org
marnen@marnen.org