UNIX : Switching users in a shell script?

aravindts · 10-12-2007, 05:27 AM

Hi All,

I want to switch between users from within a shell script.

I am executing a shell script as user1 and I need to switch to user2, execute some commands in user2’s envt and return back to user1.
Both user1 and user2 do not have root privileges.

Any pointers would be helpful.

Thanks in advance,
Aravind.T.S.

santana · 10-12-2007, 08:52 AM

Since no one helped you I offer an idea...

You could leverage ssh to do something like this. Make sure you have sshd installed and running on the system. ssh can run a single command on a remote(or local) system and get the output back to your local system.

Syntax:
ssh user@systemname 'command_and_arguments'

You must put the entire remote command and its arguments in quotes if it contains any special characters that the local shell might otherwise try to interpret (you want them to be interpreted by the remote shell). Doing this alone may not work since ssh will expect you to enter a password to login however you can work around this by setting up automatic logins by exporting ssh keys to get around the password prompt. specifically follow these instructions:

http://www.bluegum.com/Software/ssh-auth.html

good luck, and if you fuind a better way please share!!!

anomie · 10-12-2007, 09:25 AM

Quote:

Originally Posted by aravindts

I am executing a shell script as user1 and I need to switch to user2, execute some commands in user2’s envt and return back to user1.

How about setting up user1 as a sudoer (so that he can execute all or certain commands as user2)?

makyo · 10-12-2007, 09:36 AM

Hi.

I am able to do this interactively -- provided I know the alternate user's password:

Code:

#!/usr/bin/env sh

# @(#) s1       Demonstrate switching user in script.

set -o nounset
echo

debug=":"
debug="echo"

## Use local command version for the commands in this demonstration.

echo "(Versions used in this script displayed with local utility "version")"
version bash

echo

echo " Starting user:"
whoami

echo
echo " Prepare to enter password for tiller, and run in sh:"
su - tiller sh

echo
echo " Final user:"
whoami

exit 0

Producing:

Code:

% ./s1

(Versions used in this script displayed with local utility version)
GNU bash, version 2.05b.0(1)-release (i386-pc-linux-gnu)

 Starting user:
makyo

 Prepare to enter password for tiller, and run in sh:
Password:
sh-2.05b$ whoami
tiller
sh-2.05b$ exit
exit

 Final user:
makyo

cheers, makyo

student04 · 10-12-2007, 11:08 AM

Try playing with the command "login". I read it can do that for you in the man pages, but couldn't work it in my terminal because I run bash straight out, and not sh (what it's asking for as the "login shell").

-AM

ph0rty · 09-07-2012, 03:24 AM

Quote:

Originally Posted by aravindts

Hi All,

I want to switch between users from within a shell script.

I am executing a shell script as user1 and I need to switch to user2, execute some commands in user2’s envt and return back to user1.
Both user1 and user2 do not have root privileges.

Any pointers would be helpful.

Thanks in advance,
Aravind.T.S.

===========================

1. As user1, you would need to know the password of user2
su - <user2> -c "command/you/want/to_execute -options ; ./another_command | filtered output >> withredirection"

2. create an ssh key (without passphrase) for user1, put the public key into user2 ~/.ssh/authorized_keys, command now looks like this - to be run as user1 - (and does not require user1 to know user2 password)
ssh <user2>@localhost "command/you/want/to_execute -options ; ./another_command | filtered output >> withredirection"

3. if you want the output of command to be owned by user1, change to:
ssh <user2>@localhost "command/you/want/to_execute -options ; ./another_command | filtered output" >> withredirection

4. you can go and setup sudo as well (beyond the scope of this) , but assuming you dont have root, use the above, if you have root or can get root to add for you, variations of:
sudo -- su - <user2> -c "command/you/want/to_execute -options ; ./another_command | filtered output >> withredirection"

Have fun