For problem A only use sed, grep -f and bash (to launch them) Problem A: sed and
ID: 3888133 • Letter: F
Question
For problem A only use sed, grep -f and bash (to launch them)
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.
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.
for problem B only use sed, cat, sort, uniq -c, and bash (to launch them)
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.
lastlog1.out
Username Port From Latest
root pts/6 crush.cs.utsarr. Tue Aug 15 10:52:33 -0500 2017
daemon **Never logged in**
bin **Never logged in**
sys **Never logged in**
sync **Never logged in**
games **Never logged in**
man **Never logged in**
lp **Never logged in**
mail **Never logged in**
news **Never logged in**
uucp **Never logged in**
proxy **Never logged in**
www-data **Never logged in**
backup **Never logged in**
list **Never logged in**
irc **Never logged in**
gnats **Never logged in**
nobody **Never logged in**
libuuid **Never logged in**
syslog **Never logged in**
messagebus **Never logged in**
landscape **Never logged in**
sshd **Never logged in**
ubuntu pts/0 mangw.cs.utsarr. Wed Dec 16 16:49:41 -0600 2015
statd **Never logged in**
usbmux **Never logged in**
lastlog2.out
Username Port From Latest
root pts/0 crush.cs.utsarr. Tue Aug 15 09:47:07 -0500 2017
daemon **Never logged in**
bin **Never logged in**
sys **Never logged in**
sync **Never logged in**
games **Never logged in**
man **Never logged in**
lp **Never logged in**
mail **Never logged in**
news **Never logged in**
uucp **Never logged in**
proxy **Never logged in**
www-data **Never logged in**
backup **Never logged in**
list **Never logged in**
irc **Never logged in**
gnats **Never logged in**
nobody **Never logged in**
libuuid **Never logged in**
syslog **Never logged in**
messagebus **Never logged in**
landscape **Never logged in**
sshd **Never logged in**
ubuntu pts/0 mangw.cs.utsarr. Wed Dec 16 16:49:41 -0600 2015
statd **Never logged in**
usbmux **Never logged in**
Explanation / Answer
In the question logs for 2 servers, fox01 and fox 02 given.
/usr/local/courses/clark/cs3423/2017Fa/Proj2/lastlog1.out
/usr/local/courses/clark/cs3423/2017Fa/Proj2/lastlog2.out
Sample log file looks like
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**
xyz2017 pts/12 175.220.54.98 Mon Aug 20 08:15:30 -0600 2014
-> Copy those last log file to your home directory.
(syntax for coping multiple file to a directory : cp file1 file2 .... <directory>)
cp /usr/local/courses/clark/cs3423/2017Fa/Proj2/lastlog1.out /usr/local/courses/clark/cs3423/2017Fa/Proj2/lastlog2.out /home/user123/code
you need to provide your code directory in the place of /home/user123/code. To know about your current working directory you can use pwd command.
-> p2aDollar.sed : Procuces a user id file with $ after the user ids
create a file named p2aDollar.sed and write below command line in it.
grep -v '2017$' lastlog1.out | awk '{print $1}' | sed 's/.*/&$/' > used_id1
used_id file will contain used ids like below
> cat user_id
ums562$
xyz222$
fernandez$
ytang$
xyz2017$
Explanation :
grep '2017$' sample.txt will return the lines which are ending with 2017, if we will add -v option the result get reversed.
grep -v '2017$' sample.txt , provides the lines which doesn't contain 2017 at the last.
Then the output of grep is passed to awk '{print $1}' through pipe line which returns only the first column(user id).
Then the output is passed to sed 's/.*/&$/ . " /.*/" searches for any line containing any character and then replace with $ added to the search result. & represent the last search result which is the user id itself and replaces with userid$. $ is used for avoiding sed command to treat $ as a special character.
->p2a.sed : Procuces a user id file without $ after the user ids.
create a file named p2aDollar.sed and write below command line in it.
grep -v '2017$' lastlog2.out | awk '{print $1}' > user_id2
the above command will get the user id and store it into user_id2 file without any $ at the end.
->p2a.bash
(create a bash file p2a.bash)
#!/bin/bash
sh p2aDollar.sed
sh p2a.sed
grep -f user_id1 user_id2 > p2a.out
In the above script user_id1 is created with usernames and combined with $. Then the user_id2 which contain only the user name list.
Finally in the grep command we are passing the search pattern in a file which is username$ and searching in user_id2 file will provide the exact match. The result then stored into p2a.out.
cat p2a.out
ums562
xyz222
fernandez
ytang
xyz2017
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