Getting $USER inside shell script when running with sudo?

Question

How do I get the correct $USER if I run a shell script with sudo ?

I run them as postinstall scripts in a Mac install package, where they are being sudo-ed automatically, but I need to do stuff with the username.

$HOME is correct, though. The inelegant method would be to extract the name from the home path, but I wonder if there is a natural way to do this.

I can't influence the way the scripts are being called, as it's an automatic call inside the installer.

Answer 1

On my system the variable $SUDO_USER is set to the caller's user name.

You shouldn't extract the username from the ${HOME} variable directly. It's being configured and not calculated. To Extract the username you could take a look into /etc/passwd file, but this is very system dependent, e.g. sometimes you have to look into a LDAP directory or the entries are propagated through NIS ...

Answer 2

You can use $(logname), which returns your login name even if you are currently sudoing.

Answer 3

Inspect the variable SUDO_USER.

http://www.gratisoft.us/sudo/man/sudo.html#environment

Another way to get the user is via the who command. This is useful sometimes when you don't care if the user has sudo'd or not.

who -m | awk '{print $1;}'

Answer 4

SUDO_USER isn't portable. It's unset on Fedora 17.

The $USER and $UID variables aren't predictable when invoking sudo either. Some distros report the sudoer, others report the root user.

It's by no means perfect, but you could use test -w ~root && echo I have write access to ~root.