id [OPTION]... [USERNAME]
Print user and group information for the specified USERNAME, or (when
USERNAME omitted) for the current user.
-a ignore, for compatibility with other versions
-Z, --context
print only the security context of the current user
-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
--help display this help and exit
--version
output version information and exit
Without any OPTION, print some useful set of identified information.