This appears to be a simple question, but I have never gotten round to
find out due to webmin.

How do you list the members of group from the command line?

/voipfc

On Jun 20, 6:59 am, voipfc <voi...@googlemail.com> wrote:
> This appears to be a simple question, but I have never gotten round to
> find out due to webmin.
>
> How do you list the members of group from the command line?

The simplest way would be to
cat /etc/group
and look at the fourth field

A bit more complex would be
grep 'groupname' /etc/group
and look at the fourth field

And, you could
awk -F : '$1 ~ /groupname/ { print $4}' /etc/group
and look at the output

On 2007-06-20, Lew Pitcher <lpitcher@teksavvy.com> wrote:
> On Jun 20, 6:59 am, voipfc <voi...@googlemail.com> wrote:
> The simplest way would be to
> cat /etc/group
> and look at the fourth field

All those have a problem: they don't give you all the members for a
group.

If I do this on my system:

# id
uid=1000(davide) gid=100(users)
groups=100(users),11(floppy),17(audio),18(video),1 9(cdrom)

# grep users /etc/group
users::100:

So I'm member of the group 'users' but I do not appear in the group file
associated to that group.

Davide

--
Microsoft seems to have gotten a lot of mileage out of the C2 rating for
NT with no network connection. I wonder if a B3 rating for Linux with no
power cord might be of value.

On Jun 20, 8:21 am, Davide Bianchi <davideyeahs...@onlyforfun.net>
wrote:
> On 2007-06-20, Lew Pitcher <lpitc...@teksavvy.com> wrote:
>
> > On Jun 20, 6:59 am, voipfc <voi...@googlemail.com> wrote:
> > The simplest way would be to
> > cat /etc/group
> > and look at the fourth field
>
> All those have a problem: they don't give you all the members for a
> group.
>
> If I do this on my system:
>
> # id
> uid=1000(davide) gid=100(users)
> groups=100(users),11(floppy),17(audio),18(video),1 9(cdrom)
>
> # grep users /etc/group
> users::100:
>
> So I'm member of the group 'users' but I do not appear in the group file
> associated to that group.

Actually, your results reflect a (common) problem with setup. It
appears that the "primary group" value from the various users recorded
in your /etc/password have not been carried over to your /etc/group
file.

If you are in this situation, then the process of obtaining a complete
listing for a group becomes a bit more complex. I don't think that
there is a specific tool that will answer your question in this case,
but a shell script could be crafted to do what you want.

Lew Pitcher wrote:
> On Jun 20, 8:21 am, Davide Bianchi <davideyeahs...@onlyforfun.net>
> wrote:
>> On 2007-06-20, Lew Pitcher <lpitc...@teksavvy.com> wrote:
>>
>>> On Jun 20, 6:59 am, voipfc <voi...@googlemail.com> wrote:
>>> The simplest way would be to
>>> cat /etc/group
>>> and look at the fourth field
>> All those have a problem: they don't give you all the members for a
>> group.
>>
>> If I do this on my system:
>>
>> # id
>> uid=1000(davide) gid=100(users)
>> groups=100(users),11(floppy),17(audio),18(video),1 9(cdrom)
>>
>> # grep users /etc/group
>> users::100:
>>
>> So I'm member of the group 'users' but I do not appear in the group file
>> associated to that group.
>
> Actually, your results reflect a (common) problem with setup. It
> appears that the "primary group" value from the various users recorded
> in your /etc/password have not been carried over to your /etc/group
> file.

This is NOT a problem. It is designed this way. To get a view
into all groups and "membership" ... you'll have to look at both
/etc/passwd (where just a gid for the primary is found) and
/etc/group (where you'll find gid to name mappings and supplemental
group membership).

>
> If you are in this situation, then the process of obtaining a complete
> listing for a group becomes a bit more complex. I don't think that
> there is a specific tool that will answer your question in this case,
> but a shell script could be crafted to do what you want.
>

For example (off the top of my head)... No warranties...

#!/bin/sh

#
# Sort /etc/group and /etc/passwd ALPHABETICALLY by gid
#
sort -t: +2 /etc/group >/tmp/group-sorted.out
sort -t: +3 /etc/passwd >/tmp/passwd-sorted.out

#
# Join on the gid field and cut out just the username and the gid
#
join -t: -1 4 -2 3 /tmp/passwd.sorted /tmp/group.sorted |
cut -d: -f2,8 >/tmp/primary-group.out

#
# Read the username and primary group, find supplemental groups for
# each username and do final output.
#
while IFS=: read username pgrp;do
#
# Grep supplemental groups, but remove the primary
# group if found again (that is non standard btw)
#
sgrps=`grep "[,]*${username}[,]*" /etc/group |
cut -d: -f1 | grep -v "^${pgrp}\$"`
#
# Separate groups with commas, remove trailing
# comma.
#
allgrps=`echo -e "$pgrp\n$sgrps\c" |
tr '\012' ',' | sed 's/,$//'`
#
# Output the result
#
echo "$username:$allgrps"
done </tmp/primary-group.out

On 2007-06-20, voipfc <voipfc@googlemail.com> wrote:
>
> How do you list the members of group from the command line?

Again, I'm surprised not to see this suggestion:

getent group

This does suffer from the same drawback as looking solely at /etc/group,
in that it won't tell you where a userid has his primary gid listed in
/etc/passwd but not in /etc/group. But it has the advantage that it
will list all available groups, if your box is an NIS or LDAP (pam_ldap
or nss_ldap) client.

--keith

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