php man page for groups

GROUPS(1)							   User Commands							 GROUPS(1)

NAME
       groups - print the groups a user is in

SYNOPSIS
       groups [OPTION]... [USERNAME]...

DESCRIPTION
       Print group memberships for each USERNAME or, if no USERNAME is specified, for the current process (which may differ if the groups database
       has changed).

       --help display this help and exit

       --version
	      output version information and exit

AUTHOR
       Written by David MacKenzie and James Youngman.

REPORTING BUGS
       GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
       Report groups translation bugs to <http://translationproject.org/team/>

COPYRIGHT
       Copyright (C) 2017 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.

SEE ALSO
       getent(1)

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

GNU coreutils 8.28						   January 2018 							 GROUPS(1)