id

Display current user's ID (UID), group ID (GID) and groups to which they belong

$ id

Display the current user identity as a number

$ id -u

Display the current group identity as a number

$ id -g

Display an arbitrary user's ID (UID), group ID (GID) and groups to which they belong

$ id [username]

id [OPTION]... [USER]...

Print user and group information for each specified USER, or (when USER omitted) for the current user.

-a

ignore, for compatibility with other versions

-Z, --context

print only the security context of the process

-g, --group

print only the effective group ID

-G, --groups

print all group IDs

-n, --name

print a name instead of a number, for -ugG

-r, --real

print the real ID instead of the effective ID, with -ugG

-u, --user

print only the effective user ID

-z, --zero

delimit entries with NUL characters, not whitespace;

not permitted in default format

--help

display this help and exit

--version

output version information and exit

Without any OPTION, print some useful set of identified information.

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>

Copyright © 2020 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

Full documentation <https://www.gnu.org/software/coreutils/id> or available locally via: info '(coreutils) id invocation'

Written by Arnold Robbins and David MacKenzie.