From: Robert Klemme <shortcutter@...>
Date: 2010-02-09T16:52:53+09:00
Subject: Re: Working directory for external commands

2010/2/9 Duckz King_duckz <king_duckz@yahoo.it>:
> 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?

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

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