Hello everybody,

I'm trying to find a command to get the list of existing groups, and another one to get the list of existing users. Is there any way to do it by using a simple command?.

Also, I know that the id command allows me to get the info of a specifict user, including the groups the user belongs to, but I want to know if there is some kind of command to get the list of users for a specific group (some kind of inverse of id).

Thanks in advance!

Kind regards,

Ezequiel

cat /etc/passwd and cat /etc/group will print out the users and groups respectively, though not elegantly.

cat /etc/passwd | awk -F":" '{print $1}'
cat /etc/group | awk -F":" '{print $1}'

will print just the names of the users and groups, respectively.

I am hoping someone posts an answer involving sed. I looked and could not pull the first match "^.*:" out and just print that.

sed 's/\([^:]*\):.*/\1/' /etc/passwd

but I would probably just use cut. cut -d: -f1 /etc/passwd

You don't need to cat something to awk, as awk will take a filename argument. (Known as UUOC or "Useless Use of Cat".)

cut -d: -f1,4 /etc/group might give what you wanted, kelo81, for the groups.

Well thanks guys!!! All the commands are just working ok!, the cut -d: -f1,4 /etc/group command gives me exactly what I want!

I'm gratefull for your help!

Kind regards,

Ezequiel

You are one serious geek. Props to you.

I dunno about that, but thanks.

It was mostly for the UUOC statement :-).

Hello again! I was using that command for a while (the "cut -d: -f1,4 /etc/group"), but then I realized that it was impossible to use it in real time for an automated script. I mean, it works perfect for the existing users and groups, but if you add some new users with “useradd” (for example), it won’t upgrade the file “/etc/group”!. Even if I modify the default group for a specific user with “usermod -g somegroup”, it won't upgrade the file, it will just leave the old entry.
How can I force the update of the /etc/group file? And iIf it's not possible, is there any other way to query the groups and users for each “group” in real time?
Thanks in advance for your help!!