sed append to end of a specific line

[harveyd]

What I am trying to achive is the editing of /etc/ssh/sshd_config

I have the line

AllowUsers usera userb

And I want to be able to append to the end of this line from a bash script.

I have muddled together from other sites and got the following:-

sed -e "s/^AllowUsers/\0 userc/" -i /etc/ssh/sshd_config

But this appears to add userc directly after AllowUsers and not after userb

I'm not great with sed so it's proably something simple.

Thanks in advance

[harveyd]

Ok have found the solution:-

sed -e '/AllowUsers/s/$/ userc/' -i /etc/ssh/sshd_config

Seems to work for me.

[Kloschüssel]

I don't think a further reader would understand that (it took me some time to figure this out) and you could rewrite this to:

sed -e '/AllowUsers/s/AllowUsers\(.*\)$/AllowUsers\1 newuser/g' test > test

I use here backreferences to make it more clear what the expression does and use piping to make it clear that this command also writes to the file. One could drive it further and parse each single username that is already configured by means of a sed subroutine.

sed -e '/AllowUsers/s/AllowUsers\({...}\)$/AllowUsers\1 newuser/g' test > test

Thus you could add and remove users invoking this command only.