From: felix@...
Date: 2002-03-08T13:53:14+09:00
Subject: Re: Permanently change directory after exit

>>In article <000201c1c649$31a20ae0$cbfbc9c8@guara>, "Guaracy Monteiro" <guaracybm@ig.com.br> writes:

> I need change a path inside a script and stay there
> after exit (without pipes etc). Can i do it?

> e.g.

> before:
> /home/user

> script:
> #!/usr/local/bin/ruby
> Dir.chdir('/usr/local/doc')

> after:
> /usr/local/doc

Nope.  When I first wanted to do this, it was very frustrating until I
understood why.

When a program runs, it is because some other program (the shell or a
window manager) has spawbned it as a child process.  There is no way
for the child to tell the parent to change the parent's working
directory.  This is also why the child cannot change the parent's
environment variables.

But there is a convoluted way of doing this, at least from a shell,
which may not be useful to you.  In sh or bash or ksh, "source" a
shell script with the '.' command, and it executes in the shell's
environment.  Then this new script would look like

    cd /usr/local/doc

-- just that one line, you don't need the #! first line for a dot
command.  Call the script "mycd", run it as ". ~/mycd" and the shell
will be in a different dir.

But it won't be a ruby script.  I don't rhink you can do that easily,
unless you are running a ruby shell.  I am just learning Ruby, so I am
going to suggest some psuedo-Ruby here, which might work.  Might not.
Probably needs some tweaking if it could work!

mycd.rb:

#!/usr/bin/ruby

Dir.chdir('/usr/local/doc')
kernel.exec('/bin/sh')

mycd:

exec mycd.rb

And from the command line:

. mycd

Pretty awkward.  The shell sources a single line shell script (instead
of running it as a child process) which replaces the shell with the
ruby script.  This changes the working directory, then replaces the
ruby interpreter with a shell again.  Any environment changes from the
original shell might not carry into the ultimate replacement shell.

-- 
            ... _._. ._ ._. . _._. ._. ___ .__ ._. . .__. ._ .. ._.
     Felix Finch: scarecrow repairman & rocket surgeon / felix@crowfix.com
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I've found a solution to Fermat's Last Theorem but I see I've run out of room o