We are a training institute providing training on Linux and C++ . We had around 100 students in a batch and for each of the user , a separate unix account is created.
After the batch completes , we need to remove all user accounts except few exceptions like faculty and technical staff accounts.

I already identified how to remove the user accounts but am worried how to ignore the user accounts of faculty and technical staff .

My command is as follows:

#UIDMAX will contain the minimum value used by OS for ID selection
UIDMIN=`grep "UID_MIN" /etc/login.defs`

#UIDMAX will contain the mixnimum value used by OS for ID selection
UIDMAX=`grep "UID_MAX" /etc/login.defs`

#echo $UIDMAX
#echo $UIDMIN


for i in ` awk -F: -v "min=${UIDMIN##UID_MIN}" -v "max=${UIDMAX##UID_MAX}" '{ if ( $3 >= min && $3 <=max ) print $1}' /etc/passwd`
do
userdel -r $i
done

Please suggest how to ignore faculty unix accounts so that they are ignored during the deletion process .

In the best of all worlds, you would have prepared ahead and installed your student accounts using a script and list file. That list file would provide a key into deleting only student accounts.

Failing the above, did you at least give your students and faculty different group membership? That would make this easy.

Failing ALL of the above, did you at least put faculty and student home folders in different trees?

As a last choice, can you list all of your faculty and staff IDs (of UIDs) and have your script do a fast find to skip those accounts?

Next time, plan ahead. This should be really easy, but not doing the preperation up front makes for a lot more hoop jumping at the end.

maybe in /etc/passwd you can put a comment as to whether an account is a student or faculty. then it a simple if statement in a bash script could operate on the student accounts.