I need to write a shell script to add a list of newusers in the below format

usernameassword:groupname:fullname

I am really new at Linux (Fedora Core 1), could anybody please give me a hand?

I am having trouble with
1) reading from the input file
2) saving the new users' information into the correct files

what do you mean by add new users??
do you want to add users to the system??
or just take some input and write a file??

Your input file is in this format:

usernameassword:groupname:fullname

and you need to add these users to the system, is that right?

First thing to do in your script would be:
IFS=\015
this sets the 'splitting' character to \n, so you can work with lines that have spaces. Then you could do something like this:
for x in `cat userlist.txt`
do
USER=`echo $x | cut -f 1 -d:`
PW=`echo $x | cut -f 2 -d:`
GRP=`echo $x | cut -f 3 -d:`
NAME=`echo $x | cut -f 4 -d:`
xxxx
done

The lines xxxx are the ones I can't be sure of as I don't use Redhat, but check your man pages for scripts like adduser or useradd, addgroup or groupadd. To set the passwords, you might need to install expect or find a tool that sets passwords from the command line.

Yes, I have to add new users to the system from a list of user from an input file that is formatted like this;

username:password:groupname:fullname
username:password:groupname:fullname
username:password:groupname:fullname

and so on...


I have also noticed that when a new user is added to the system their groupname is automatically created using their username.

How can I stop this??

Check the man page for useradd, you should find the help you need there.

This worked for me:

useradd -g (default group) (other options) username
e.g, to add a user 'fred' using the group 'users' (so it won't create a fred group)
useradd -g users fred