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I've tried Googling but not getting anywhere. How can I list all the members of a group called mygroup from the command-line in OS X?

$dscl . list /groups will get me all the groups...but how can i see each group's members?

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5 Answers 5

up vote 24 down vote accepted

There's no standard command that lists all members of a group in OS X, so here's a shell function which does that:

members () { dscl . -list /Users | while read user; do printf "$user "; dsmemberutil checkmembership -U "$user" -G "$*"; done | grep "is a member" | cut -d " " -f 1; }; 

Copy the above command-line to the Terminal, and then type members mygroup (where mygroup is the name of an existing group).


Some explanation for those who are interested:

There are five different ways (that I know of) that a user can be member of a group in OS X. The command dscl . -read /Groups/mygroup GroupMembership isn't guaranteed to output all, or even any, of mygroup's members, because membership also comes from users' primary group ID, membership by user's UUID, inheritance of membership from one group to another, and memberships that are calculated by the system, such as the group everyone.

So rather than trying to keep track of all those, it seems like a better idea to simply check the membership of every user on the system (using dsmemberutil), and that's what the shell function and the script below do.


This members script is equivalent to the shell function, but has nicer handling of invalid input:

#!/bin/bash

# members -- list all members of a group
#
# SYNOPSIS
#   members groupname
#
# http://superuser.com/questions/279891/list-all-members-of-a-group-mac-os-x
#  by Arne
# Expected to work on Mac OS 10.5 and newer, tested on 10.6 and 10.7.
# It could be rewritten to work on 10.4 by using "dseditgroup -o checkmember"
# instead of "dsmemberutil checkmembership".
# By using dseditgroup, the script could also be extended to handle
# other Directory Service nodes than the default local node.
#

the_group="$1"
# Input check and usage
  if [[ $# != 1 || $1 == -* || $1 =~ [[:space:]] ]]; then
    echo "Usage: ${0##*/} groupname" >&2
    echo "Lists all members of the group." >&2
    exit 64
  elif (dsmemberutil checkmembership -U root -G "$the_group" 2>&1 \
    | grep "group .* cannot be found") >&2; then
    exit 1
  fi

# Check every user
exec dscl . -list /Users \
  | while read each_username
  do
    printf "$each_username "
    dsmemberutil checkmembership -U "$each_username" -G "$the_group"
  done \
    | grep "is a member" | cut -d " " -f 1

# eof

Supplementary info:

The five ways of being a group member are:

  1. The user's PrimaryGroupID
  2. Listed in the group's GroupMembership
  3. UUID listed in the group's GroupMembers
  4. Inherited membership of group X by being a member of group Y which is listed in group X's NestedGroups
  5. Membership calculated by the system

These can be explored with commands like dscl . -read /Groups/somegroup

Example of 4: Membership of the Print Operator group _lpoperator is inherited by members of the Print Administrator group _lpadmin, and membership of that group is inherited by the members of the admin group.

Example of 5:

$ dscl . -read /Groups/netaccounts Comment
Comment:
 Group membership calculated by system
 Accounts from a remote directory server
$ 

SEE ALSO
    id(1), dscl(1), dsmemberutil(1), dseditgroup(8), DirectoryServiceAttributes(7), uuid(3)

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1  
This is the kind of peculiarities that I have in mind when I tell people that while OS X is mostly beautiful on the surface it's got some nasty stuff hidden underneath the covers. –  Stefan Schmidt May 10 '12 at 15:40
    
+1: This works solidly. Merci. –  Slipp D. Thompson Jan 18 '13 at 23:20
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Note: This was my initial answer, written before I realized this answer still gives an incomplete result. (For example, it finds no members of the everyone group!) So I wrote a better answer, which includes a script that lists all members of a group in OS X.


mygroup's GroupMembership property can be printed with dscl like this:

dscl . -read /Groups/mygroup GroupMembership

But this isn't guaranteed to output all (or even any) of the group's members. What's missing are the users who are member of the group only by having it as their primary group ID.

A common example of this in OS X are regular login accounts, which have staff (group 20) as their primary group, but are not listed in the GroupMembership property of the staff group.

Those users can be found by searching for the numeric primary group ID (gid) like this example for the staff group (gid 20):

dscl . -list /Users PrimaryGroupID | grep " 20$"

and the numeric gid (PrimaryGroupID) of mygroup is found by:

dscl . -read /Groups/mygroup PrimaryGroupID
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You can use:

dscacheutil -q group -a name admin

or:

dscacheutil -q group -a name staff

etc.

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dscl . -read /Groups/[groupname] | grep GroupMembership

BE AWARE: The command above does not always display a complete list of ALL group members. E.g. for the group "staff" you only get "root" as a group member which is incomplete. To check it use one of the following commands as a default user (NOT "root"): id -Gn OR groups

As a result you will see all groups your default logged user is a member of. One of them should be "staff". Thus, besides "root" there are more members of the group "staff", which are not listed by the command dscl . -read /Groups/[groupname] | grep GroupMembership. The same goes for the command dscacheutil -q group -a name staff which also suggests you that only "root" is a member of the group "staff", which is obviously incomplete.

The only reliable method to get really ALL members of a group in the terminal on OSX is already provided here by Arne Stenström. This is using his shell function resp. his shell script. Both works great!

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that's it! thanks! –  Meltemi May 6 '11 at 2:17
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Here is an implementation for this problem which was derived from an implementation in a related discussion. The routine is somewhat generic, with a directory service lookup hook for any specific platform/architecture, so it can be used without modification on a heterogenous network. We've installed a symbolic link to this utility named zed. Other origins for this implementation are mentioned in the attribution section of the script. This tool is intended to be run on at least OSX, HP-UX, linux, and SunOS, but hasn't been tested on SunOS and HP-UX. The script was tested as far as possible on Ubuntu Linux 12.04 and Mavericks OSX 10.9.1. The output of this script matches the output for the first shell script implementation for this problem, and is therefore considered correct.

#!/usr/bin/perl
#
# Lists members of all groups, or optionally just the group
# specified on the command line
#
# Date:         12/30/2013
# Author:       William H. McCloskey, Jr.
# Changes:      Added logic to detect host type & tailor subset of getent (OSX)
# Attribution:
#   The logic for this script was directly lifted from Zed Pobre's work.
#     See below for Copyright notice.
#   The idea to use dscl to emulate a subset of the now defunct getent on OSX
#     came from
#       http://zzamboni.org/\
#         brt/2008/01/21/how-to-emulate-unix-getent-with-macosxs-dscl/
#     with an example implementation lifted from
#       https://github.com/petere/getent-osx/blob/master/getent
#
# Copyright © 2010-2013 by Zed Pobre (zed@debian.org or zed@resonant.org)
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#

use strict; use warnings;

$ENV{"PATH"} = "/usr/bin:/bin";

# Only run on supported $os:
my $os;
($os)=(`uname -a` =~ /^([\w-]+)/);
unless ($os =~ /(HU-UX|SunOS|Linux|Darwin)/)
    {die "\$getent or equiv. does not exist:  Cannot run on $os\n";}

my $wantedgroup = shift;

my %groupmembers;

my @users;

# Acquire the list of @users based on what is available on this OS:
if ($os =~ /(SunOS|Linux|HP-UX)/) {
    #HP-UX & Solaris assumed to be like Linux; they have not been tested.
    my $usertext = `getent passwd`;
    @users = $usertext =~ /^([a-zA-Z0-9_-]+):/gm;
};
if ($os =~ /Darwin/) {
    @users = `dscl . -ls /Users`;
    chop @users;
}

# Now just do what Zed did - thanks Zed.
foreach my $userid (@users)
{
    my $usergrouptext = `id -Gn $userid`;
    my @grouplist = split(' ',$usergrouptext);

    foreach my $group (@grouplist)
    {
        $groupmembers{$group}->{$userid} = 1;
    }
}

if($wantedgroup)
{
    print_group_members($wantedgroup);
}
else
{
    foreach my $group (sort keys %groupmembers)
    {
        print "Group ",$group," has the following members:\n";
        print_group_members($group);
        print "\n";
    }
}

sub print_group_members
{
    my ($group) = @_;
    return unless $group;

    foreach my $member (sort keys %{$groupmembers{$group}})
    {
        print $member,"\n";
    }
}
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