Working directory for external commands

Ruby
1

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:

git = GitWrapper.new
puts git.status

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:

def status()
    Dir.chdir("some/dir") do
        return `git status`
    end
end

which I’d rather avoid for its obvious fragility:

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

Any suggestions?

2

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,
–Â
Marnen Laibow-Koser
http://www.marnen.org
[email protected]

3

2010/2/9 Duckz King_duckz [email protected]:

[/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

4

@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 K.:
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).

5

Albert S. 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,
–Â
Marnen Laibow-Koser
http://www.marnen.org
[email protected]

6

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.