Problem A: sed and grep -f We need a new mechanism to identify accounts that haven't been used in a while so that we can remove the accounts.

We will use the lastlog tool to get information of the last time someone logged in; however, it just handles one server.

Please note that lastlog returns a result similar to this:

ums562 **Never logged in**

xyz222 pts/3 173.227.72.99 Sun Aug 7 11:39:56 -0500 2015

fernandez pts/11 n0000d193.cs.uts Wed Jan 13 11:13:49 -0600 2016

rslavin pts/2 104.218.77.194 Tue Aug 15 10:11:37 -0500 2017

clark pts/8 172.24.141.44 Fri Aug 18 13:07:29 -0500 2017

ytang **Never logged in**

In the example above, the following users meet the criteria: ums562, xyz222, fernandez, and ytang. The result file should only contain user IDs. The intersection of those result files gives us the people who didn't log into both of those servers during the desired time. Matching on 2017. Where is the 2017 we want to match which indicates that the user logged in during 2017? If we just match "2017", it could match actual login IDs that contain 2017 who haven't logged in during 2017. Intersection. Use grep -f to help with getting the intersection. Unfortunately, some login IDs like "lp" could match an id like "lpt913". There are several ways to avoid this problem. Consider having two different sed scripts (one for each of the lastlog?.out files). One of the scripts could produce output which tell the pattern to match to the end of the line: ytang$ lp$ The other sed script produces user IDs without the "$". Now the pattern lp$ doesn't match lpt913.

Problem B: sed, cat, sort, and uniq -c

For this problem, we will want to get the same result, but with a different approach. Using one of the sed scripts from problem A, we can produce two files of user IDs that either have not logged in or haven't logged in during 2017 (i.e., we won't have a pattern like "lp$" in our files). Suppose we cat those files together and sort them. We can use uniq -c to get a count of each unique value We can then use sed to include only user IDs with a count of 2 and also remove the count. Although not required, you probably should diff the outputs of the two solutions. Note that you may have to sort the output of problem A before doing the diff.

In the end, we should turn in the following files:

p2aDollar.sed produces a user ID file as described above with a $ after the user IDs for use as a pattern file

p2a.sed produces a user ID file as described above. It doesn't have the dollar sign in the output.

p2a.bash bash file for running problem A. The final result should be placed in "p2a.out".

p2b.sed removes text lines containing 1 for the count. It also removes the count values of 2 to leave just the user IDs.

p2b.bash bash file for running problem B. The final result should be placed in "p2b.out". This uses p2a.sed, sort, uniq, and p2b.sed.

However, the trick is to not use awk when completing these.