To find a user's UID or GID in Unix use the id command.

To find a specific user's UID at the Unix prompt enter:

id -u username

Replace username with the appropriate user's username.

To find a user's GID at the Unix prompt enter:

id -g username

If you wish to find out all the groups a user belongs to instead enter:

id -G username

If you wish to see the UID and all groups associated with a user enter id
without any options as follows:

id username