Shell Programming and Scripting

I have a requirement to change user inside a shell script and execute group of commands. I have done it many times earlier but never came across the issue with exporting variables. Strangely if a var is exported afetr su, it is not working where as if it is does outside su, it works. Another issue I noticed was with variable in for loop. Also I didnt have these problems with many other commands inside su .

Code:

#!/bin/sh
#ident  "@(#)Test script"
#set -x
id
var0=123
su - user1<<EOF
id
var1='123'
export var2=345
echo "var0 is $var0"
echo "var1 is $var1"
echo "var2 is $var2"
EOF

Here is the output am getting where var1 and var2 is blank.

Would really appreciate your help as am clueless with what's happening and my options are exhausted

The contents (including those variables) of the heredoc are expanded by the parent shell.

Regards,
Alister

sorry for my ignorance. What does that mean?

is it not possible to do it this way?

Please post what Operating System and version you are running so we can work out what Shell /bin/sh is (unless you can tell us).

What @alister is saying is that the environment variables in the "Here Document" (the bit between <<EOF and EOF) are evaluated by the calling Shell BEFORE the su - runs.

I can't think of an Operating System where the script would work at all because su - should prompt for a password. ... Unless you are logged in as root ?

There are techniques to do what I think you want to do, but let's find out what you actually want the script to do? Are you running as root ?

I am using Redhat Linux 2.6.32-220.4.1.el6.x86_64 and is logged in as root


The final idea is to login as root and su to some other id and run installation scripts. Those installation script need to access some variables and hence trying to set those.

As I mentioned, its not only failing in setting variables but also thing like below are also not working

Code:

for filestring in `cat $SRCDIR/install.control | grep -v "^#"`
do
echo "FILESTRING=${filestring}"
done

Can you please advise any other technique to accomplish this?

When you run that script, it promptly exports var2=345, guaranteeing that any child processes it creates will have this variable in their environments.

Then, it finishes and ceases to exist without creating any child processes. Meaning, the variable was never set anywhere except inside that script.

Children inherit exported values from their parents. Running a script doesn't set values in your own shell. Try sourcing the script instead, which runs it without creating a new shell. source ./scriptname

As i mentioned in the original post, i understand that children inherit exported values from parents, because if i move that export outside su, am still able to access those values

However am looking for ways to make this work inside heredoc. Or is there any alternate way of accomplishing this?