id - print real and effective user and group IDs
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
print only the security context of the current user
print only the effective group ID
print all group IDs
print a name instead of a number, for -ugG
print the real ID instead of the effective ID, with -ugG
print only the effective user ID
--help display this help and exit
output version information and exit
Without any OPTION, print some useful set of identified information.
Written by Arnold Robbins and David MacKenzie.
Report id bugs to firstname.lastname@example.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report id translation bugs to <http://translationproject.org/team/>
Copyright © 2013 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://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.
The full documentation for id is maintained as a Texinfo manual. If the info and id programs are properly installed at your site, the command
info coreutils 'id invocation'
should give you access to the complete manual.