Shell Programming and Scripting

I need to append a user to the end of a group in the /etc/group file

ftp::49:user1,user2...

what I want to to add a new user to the group file so that I won't have to open it up and append manually and I can't user "usermod" it fails

this user will be coming from a variable

Be careful when tinkering with system files! If usermod fails, there will be a reason for it. Please show usermod's error messages so the audience can analyse it.
Just adding a member to a group in /etc/group may totally ignore security tools like shadow (gshadow) or other system info on which your system depends.

As for your question: How do you supply the group to be appended to? In a variable as well?

I know about the problem I just want to know how to append

If you have permission and really really understand the consequences of editing /etc/group, you want ed or ex; not sed:

Code:

Grp=<group to be modified>
Usr=<user to be added>
ed -s /etc/group <<-EOF
        /^$Grp:/s/\$/,$Usr/p
        w
        q
EOF

I tried it but it didn't work

So, you've been asked to show us the errors from usermod (but haven't done so).

Now you're saying ed doesn't work (but not showing us the errors from ed).

You're messing with the security of your system and apparently don't understand that the system doesn't believe you should be allowed to break its self defense mechanisms. We are not here to help you hack a system. If you really are trying to fix a security problem on your system and you have the rights to do so, we may be able to help if you'll explain the errors you're getting. Otherwise, there isn't anything we can do for you.

you don't know what your talking about, all I want to know is how to append to the end of the line