id

Print real and effective user id (uid) and group id (gid), prints information about the given user, or if no user is specified the process running it

SYNTAX
id [options]... [username]
By default, it prints the real user id, real group id, effective user id if different from the real user id, effective group id if different from the real group id, and supplemental group ids.

Each of these numeric values is preceded by an identifying string and followed by the corresponding user or group name in parentheses.

OPTIONS
The options cause `id' to print only part of the above information.

-g
--group
Print only the group id.

-G
--groups
Print only the supplementary groups.

-n
--name
Print the user or group name instead of the ID number.
Requires -u, -g, or -G

-r
--real
Print the real, instead of effective, user or group id.
Requires -u, -g, or -G

-u
--user
Print only the user id.