checking username

i have a cgi page that allows users to signup for my webmail service, but 
submitin info to a form that writes to a textfile. I need to get the 
username after it is submitted, and check it against existing system 
usernames (/etc/passwd) and sendmail virtual usernames. is this possible? 
if so, how?

also, how can i make a cron job that parses the textfile and creates a new 
user from the results? the textfile is in the format of:

username:password:gid:homedir:shell

the syntax for my adduser program is:

adduser -g 'gid' -d 'homedir' -s 'shell' -p 'password' 'username'

-- 
Matthew Harrison
Internet/Network Services Administrator
Peanut-Butter Cheesecake Hosting Services
Genstate
www.peanutbuttercheesecake.co.uk

• checking username by Matthew Harrison