How To Find Your UID From Bash

I see this question a lot in search engines requests which point to this blog. And if you’re so interested how this is done, I’m happy to explain.

Standard shell environment variables pointing to user id

Not only in bash, but in any other shell on your system, there’s quite a few standard environment variables set by default when you log in. Among them there are ones which contain your username, and so you can use them to find out the uid as well.

The variables I’m talking about are USER and USERNAME. Both of them should contain the same user name, in my example it’s greys:

ubuntu:~$ echo $USER
greys
ubuntu:~$ echo $USERNAME
greys

Knowing the username, it’s very easy to use the id command to confirm the user id:

greys@ubuntu:~$ id -u greys

1000

Bash environment variables

In Bash specifically, there’s also a few variables automatically set for your convenience so that you don’t have to figure UID based on the username.

In fact, there are three variables which you will find useful:

• UID – your user ID
• EUID – your effective user ID
• GROUPS – array of all the Unix groups you belong to

Here is how to show the values of these variables:

ubuntu$ echo $UID
1000
ubuntu$ echo $EUID
1000
ubuntu$ echo $GROUPS
113