How To Find Out User ID in Unix

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There's quite a few ways to confirm a user ID (uid) in Unix.

id command

This is probably one of the easiest ways to find out a uid of a particular user in your system:

# id -u greys
500

The most common way of using the id command is even simpler, and it gives you all the information about a user you may need:

# id greys
uid=500(greys) gid=500(greys) groups=500(greys)

This not only shows you the user id (uid), but also confirms user's group id (gid) and all the rest Unix groups a user belongs to.

getent

Another way to get information about a user (including uid) is to use the getent command:

# getent passwd greys
greys:x:500:500:Gleb Reys:/home/greys:/bin/bash

In this example, greys is my username, 500 is the uid, and the second 500 in this line is my Unix group id (gid).

/etc/passwd file

If you know that the user you're looking at is a local user (it is created on the local Unix system of yours), you can grep for it in /etc/passwd file directly:

$ grep greys /etc/passwd
greys:x:500:500:Gleb Reys:/home/greys:/bin/bash