topic Environment variable changes in a csh script in Operating System - HP-UX

Environment variable changes in a csh script

TD Clark — Fri, 12 Apr 2002 21:45:43 GMT

We have database environment variables set as part of our .cshrc for a login. When that same person changes his environment variables and runs a csh script the csh script reverts his changed environment variables back to the same that .cshrc sets. Any ideas on this one? Thanks all!

Re: Environment variable changes in a csh script

Dave La Mar — Fri, 12 Apr 2002 22:07:28 GMT

Unless they are set in the script, when you invoke another shell it will use .cshrc.

My .02. Been burned by this.

Best of luck.
dl

Re: Environment variable changes in a csh script

James R. Ferguson — Fri, 12 Apr 2002 22:23:09 GMT

Hi Todd:

You need to set and export the environmental variables you want visible:

# setenv MYTHING myvalue

Regards!

...JRF...

Re: Environment variable changes in a csh script

David Lodge — Sat, 13 Apr 2002 06:43:37 GMT

The problem here is called inheritance. A process may inherit its environment from its parent but can pass nothing back.

This is why you have the differences between running a shell and sourcing a shell.

When you 'run' a shell script, a new copy of the shell is spawned and the script is run in this new spawned - ie no effect to the environment of the current shell.

When you 'source' a shell script, it is loaded and executed in the current shell - therfore it will effect the current environment.

For example (using /usr/bin/sh - csh is evil and shouldn't be used :-)

$ cat env.sh
#!/usr/bin/sh
FRED="a value"
$ FRED=""
$ ./env.sh
$ echo ${FRED}

$ . ./env.sh
$ echo ${FRED}
a value
$

It's similar in csh - except you can use the keyword 'source' instead of a . eg:
% source ./env.sh
% echo $FRED
a value
%

HTH

dave