64

I've recently been creating new users and assigning them to certain groups. I was wondering if there is a command that shows all the users assigned to a certain group? I have tried using the 'groups' command however whenever I use this it says 'groups: not found'

  • 3
    That is the groups command. It is unlikely that you do not have it on Linux, since it is part of coreutils. – Thomas Dickey Nov 6 '15 at 11:50

10 Answers 10

40

You can use grep:

grep '^group_name_here:' /etc/group

This only lists supplementary group memberships, not the user who have this group as their primary group. And it only finds local groups, not groups from a network service such as LDAP.

  • 5
    Does not work with centralized authentication. – Maxim Egorushkin Nov 16 '17 at 17:04
  • 1
    This could be really confusing probably because of primary/secondary difference. I think this should be avoided in favor of sudo lid -g {group}.I have a system where this answer lists 8 users in a group whereas sudo lid -g {group} lists 10. – DKroot Jul 25 '18 at 15:35
81

I prefer to use the getent command ...

Since getent uses the same name service as the system, getent will show all information, including that gained from network information sources such as LDAP.

So for a group, you should use the following ...

getent group name_of_group

where name_of_group is replaced with the group you want to look up. Note that this only returns supplementary group memberships, it doesn't include the users who have this group as their primary group.

There are a whole lot of other lookups that you can do ... passwd being another useful one, which you'll need to list primary groups.

  • 1
    The other answers doesn't apply if you are not administrator and the group info is stored in other server. – Andrés Alcarraz Feb 4 '18 at 20:37
  • 1
    This could be really confusing probably because of primary/secondary difference. I think this should be avoided in favor of sudo lid -g {group}.I have a system where this answer lists 8 users in a group whereas sudo lid -g {group} lists 10. – DKroot Jul 25 '18 at 15:36
12

Easier to do groups [username]

If you want to list all local users and their local groups you can do

cat /etc/passwd | awk -F':' '{ print $1}' | xargs -n1 groups

If you get "groups: command not found", it is likely you've edited your environmental path for the worse, to reset your path do PATH=$(getconf PATH)

  • It works for a particular group if | grep {group} is added and gives the correct answer unlike getent group name_of_group or grep '^group_name_here:' /etc/group – DKroot Jul 25 '18 at 15:39
  • 1
    Instead of cat /etc/passwd, you should use gentent passwd so users in nis/ldap would still be listed. The only drawback is that it can take quite a while. – Brian Minton Jun 5 at 21:13
7
groupmems -g groupname -l

lists all users in the named group.

  • Note that groupmems is part of the shadow utils used on most Linux distros, however groupmems is currently absent from Debian and derivative (a bug now fixed but not included in any release yet (as of Nov 2016)) – Stéphane Chazelas Nov 6 '16 at 22:14
  • 2
    Also note that groupmems only deals with groups in /etc/group (not the ones in LDAP or other user database) and requires superuser privileges as it tries to open /etc/gshadow. – Stéphane Chazelas Nov 6 '16 at 22:28
  • Despite the caveats mentioned above, this command is ideal for certain situations because it doesn't require additional parsing of the output (i.e. cut and friends). – bonh Oct 23 '17 at 14:55
  • This could be really confusing probably because of primary/secondary difference. I think this should be avoided in favor of sudo lid -g {group}. I have a system where this answer lists 8 users in a group whereas sudo lid -g {group} lists 10. – DKroot Jul 25 '18 at 15:42
5

I am surprised nobody mentioned

id <user>

This command will give a list of groups the user is in.

  • 3
    Because - contrary to the title - the questioner wanted to know the users within a given group, not the groups of a given user, as detailed in the question. I now rephrased the title to match the contents. – Dubu Nov 9 '15 at 10:10
  • Aaah, I see. I should have read the question text better. Thanks. – Alex Nov 9 '15 at 10:11
3

groups command prints group memberships for a user. You can use lid command to list users in a group like:

# lid -g <groupname>
  • 4
    lid is part of libuser, which is not installed by default on many distributions. – Chris Down Nov 6 '15 at 11:57
2

OP phrased the question to exclude the possibility of using the groups command. Since that is part of coreutils on Linux, either (a) it was removed, or (b) OP is mistyping the name.

OP could have used groups like this, for instance:

for name in $(cut -d: -f1 /etc/passwd);do groups $name|grep -w sudo|awk '{print $1;}';done

One suggested answer just grep's for the group name in /etc/group. Sometimes that works as intended.

A slightly better use of grep takes into account the syntax of /etc/group:

group_name:password:GID:user_list

so that only the part before the first colon is a valid group-name. A plain grep without regard to syntax can (and will) pick up misleading matches from the file. Use regular expressions to make the grep match exactly what is needed:

grep -E '^users:' /etc/group |sed -e 's/^.*://'

or using a shell variable:

grep -E '^'$groupname':' /etc/group |sed -e 's/^.*://'

However, that only lists those not in a default group. To add those, you need to take into account the password file, e.g., by extracting the group-id number from /etc/group, and printing the users whose default group matches from /etc/passwd, e.g.,

grp=$(awk -F: '$1 ~ /^users$/ {print $3; }' </etc/group)
awk -F: '$4 ~ /^'$grp'$/ { print $1; }' </etc/passwd

You could do the same thing using just grep and sed, but it is more work than using awk.

Another suggested answer proposed using getent, which also is likely to be on a Linux machine (with Debian, it is part of GNU libc). However a quick check of that shows it providing only the /etc/group content.

I (like most) do not have libusers or lid installed, so I cannot comment on whether it satisfies OP's conditions.

There is also the id program, which gives group information. Someone might expand on that as a possible answer.

  • Or just sed -n "s/^$groupname:.*://p" /etc/group but that could still report wrong results if the group name contains RE operators (. for instance is not uncommon in group names). – Stéphane Chazelas Nov 6 '16 at 21:54
  • GNU getent will also query LDAP/NIS... though possibly not when enumeration is explicitly disabled for the group database. – Stéphane Chazelas Nov 6 '16 at 21:56
  • Note that groups would not help as it lists the groups a given user is member of as opposed to the list of members of a given group. – Stéphane Chazelas Nov 6 '16 at 22:01
2

Works like a charm:

cut -d: -f1,4 /etc/passwd | grep $(getent group <groupname> | cut -d: -f3) | cut -d: -f1
  • Unlike the accepted answer of @ARG, this command lists the users having <groupname> as their primary group – Bhavik Mar 7 '17 at 5:28
  • this should be the accepted answer – Nikolay Nenov Jun 8 '17 at 10:58
  • 1
    I disagree. Because it reads users in /etc/passwd, this will not work with other nsswitch modules that access LDAP etc. – Ivan Vučica Oct 25 '17 at 11:00
  • Didn't work correctly for me: I got 4 members in a group whereas sudo lid -g lists 8. @Bhavik The accepted answer is not correct either. – DKroot Jul 25 '18 at 15:54
2

Some will tell you to install libuser (for 'lid') or members (for 'members'). But building upon the answer https://unix.stackexchange.com/a/349648/77959 which handled this issue with login group membership I found another group not being covered by that script. So - here's the best of both approaches combined:

#!/bin/bash
if [ $# -eq 1 ]; then
        list_a=`cut -d: -f1,4 /etc/passwd | grep $(getent group "$1"| cut -d: -f3) | cut -d: -f1`
        list_b=`getent group "$1"|cut -d: -f4|sed 's/,/\n/g'`
        echo -e "$list_a\n$list_b"|grep -v "^$"|sort|uniq
else
        echo "pass me a group to find the members of"
fi
  • It worked correctly on my system unlike answers involving getent or grep '^group_name_here:' /etc/group – DKroot Jul 25 '18 at 15:58
0

This modification of user3717722 approach will list groupmembers in an NIS database:

ypcat passwd | cut -d: -f1,4 | grep $(getent group <groupname> | cut -d: -f3) | cut -d: -f1

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.