Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!xzaphod!michael
From: michael@xzaphod.uucp (Michael R. Miller)
Newsgroups: comp.unix.questions
Subject: Re: using cd command in a file
Summary: script won't work
Message-ID: <1991May27.170005.12870@xzaphod.uucp>
Date: 27 May 91 17:00:05 GMT
References: <1991May20.201923.27920@garfield.ncat.edu> <9105230900.22@rmkhome.UUCP>
Reply-To: michael@xzaphod.UUCP (Michael R. Miller)
Organization: XZaphod in Rockville, MD
Lines: 47

In article <9105230900.22@rmkhome.UUCP> rmk@rmkhome.UUCP (Rick Kelly) writes:
>In article <1991May20.201923.27920@garfield.ncat.edu> muquit@garfield.ncat.edu (MUHAMMAD A. MUQUIT) writes:
>>In article <1991May20.155136.25162@ux1.cso.uiuc.edu> Charles Blair writes:
>>>
>>>   I would like to get to a directory /me/A/B/C/D by just typing j.  I tried
>>>creating a file j with cd /me/etc in it, then chmod +x j.  It didn't work.
>>>Thanks in advance.  I'm sure I'm overlooking something well-known.
>>
>>You can do the job if you put this line in your .login file:
>>     alias j 'cd /me/A/B/C/D'
>>
>>I'm also curious why your way didn't work.  I think  there're lots of gurus
>>out there to answer this.
>
>A two line script would do it.
>
>#!/bin/sh
>cd /me/A/B/C/D
>
>Then chmod +x scriptname.
>
>Rick Kelly	rmk@rmkhome.UUCP	frog!rmkhome!rmk	rmk@frog.UUCP

A script won't work because "cd" is a "built in" command in every shell
I've heard of.

What happens when you run the script is your shell forks a copy of itself
which then runs the commands in the script.  The CHILD shell does the "cd"
command.  Then the CHILD shell exits.  The shell that "knew" about the
directory change has disappeared along with the directory change itself.
The parent process (shell) still has its working directory set as it was
prior to your script running.  Nothing constructive has happened except
another process has run and some files were opened and closed causing
updates to buffers to possibly occur inside the kernel.

A modification to the script command could be:

#!/bin/sh
exec $SHELL -c "cd /me/A/B/C/D"

assuming the SHELL environment variable is set to the path to the default
shell you want to use (eg. /bin/sh).  This is not the most efficient way
of doing this.  If your shell supports aliases (/bin/ksh, /bin/csh,
/bin/zsh), use it.

Michael R. Miller
uunet!xzaphod!michael