How do I use su to execute the rest of the bash script as that user?

user_155823 0
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I've written a script that takes, as an argument, a string that is a concatenation of a username and a project. The script is supposed to switch (su) to the username, cd to a specific directory based upon the project string.

I basically want to do:

su $USERNAME;  
cd /home/$USERNAME/$PROJECT;  
svn update;

The problem is that once I do an su... it just waits there. Which makes sense since the flow of execution has passed to switching to the user. Once I exit, then the rest of the things execute but it doesn't work as desired.

I prepended su to the svn command but the command failed (i.e. it didn't update svn in the directory desired).

How do I write a script that allows the user to switch user and invoke svn (among other things)?

user-permissions su sudo permissions bash
9 Answers

The trick is to use "sudo" command instead of "su"

You may need to add this 

username1 ALL=(username2) NOPASSWD: /path/to/svn

to your /etc/sudoers file

and change your script to:

sudo -u username2 -H sh -c "cd /home/$USERNAME/$PROJECT; svn update"

Where username2 is the user you want to run the SVN command as and username1 is the user running the script.

If you need multiple users to run this script, use a %groupname instead of the username1

user_1801740

You need to execute all the different-user commands as their own script. If it's just one, or a few commands, then inline should work. If it's lots of commands then it's probably best to move them to their own file.

su -c "cd /home/$USERNAME/$PROJECT ; svn update" -m "$USERNAME"
user_39780

Use sudo instead

EDIT: As Douglas pointed out, you can not use cd in sudo since it is not an external command. You have to run the commands in a subshell to make the cd work.

sudo -u $USERNAME -H sh -c "cd ~/$PROJECT; svn update"


sudo -u $USERNAME -H cd ~/$PROJECT
sudo -u $USERNAME svn update

You may be asked to input that user's password, but only once.

user_1190050

It's not possible to change user within a shell script. Workarounds using sudo described in other answers are probably your best bet.

If you're mad enough to run perl scripts as root, you can do this with the $< $( $> $) variables which hold real/effective uid/gid, e.g.:

#!/usr/bin/perl -w
$user = shift;
if (!$<) {
    $> = getpwnam $user;
    $) = getgrnam $user;
} else {
    die 'must be root to change uid';
}
system('whoami');
user_2376880
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