'cd' ing inside a shell script

[Bill Campbell]

On Tue, Nov 07, 2006, Grant Peel wrote:
>Hi all,

>Some of my webmail users are using lots of disk space.

>I want to make a shell script, like so:

>cd /home/webmail/public_html/cgi-bin/etc/users ; du -h -d1 | grep M | sort
>-nr -k1

>and run it daily in a cronjob, mailing the results to my assistants.

>with the 'cd' at that start of the script have any adverse affect on the
>rest of the system or cronjobs? OK, will the scripot just complete and
>exit, with the 'cd' having no affect?

A cd inside a script will have no effect on anything outside of
the script.  Only brain-dead systems from Microsoft do that.

In fact, within a script, there's a safe way to do cd's that
doesn't affect the directory which can be very handy when writing
scripts that may not want to keep track of where they are:

#!/bin/sh

# do something here
(
    cd somedirecotry
    # you're now in somedirectory to do something
)
# now you're back in the original directlry.

A new shell is spawned for the process inside the parenthesis,
and any directory changes etc. will have no effect outside the
parenthesis.

Bill
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