1. Shows the members of a group; by default, all members. members is the complement of groups: whereas groups shows the groups a specified user belongs to, members shows users belonging to a specified group. Given the name of a group, members will send a space-separated list of member names to stdout. Full option parsing has been added as of this version. You can ask for primary members, secondary members, both on one line, each on separate lines. If no option is selected, prints all members on one line by default. From Debian 3.0r0 APT