Print information for USERNAME, or the current user.

-a

ignore, for compatibility with other versions

-Z, --context

print only the security context of the current 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

--help

display this help and exit

--version

output version information and exit

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

info id

should give you access to the complete manual.