Operating Systems: UNIX Shell Programming Practice Problems

The commands suggested below are not all required, nor are they the only way to solve the problem. Please try to find alternative solutions, as that will help expand your knowledge. The expected results are based on the test data files below:
# Problem Suggested Commands Expected Result
1 Display a report showing the full name of all the users currently connected, and the number of processes belonging to each of them. who, ps, finger, grep, while, wc 
bradu 2
horea 2
rares 3
2 Find recursively in a directory all ".c" files having more than 500 lines. Stop after finding 2 such files. find, wc, expr, while, break 
dir/11.c
dir/d/a/13.c
3 Find recursively in a directory, all the files with the extension ".log" and sort their lines (replace the original file with the sorted content). find, sort, mv, rm The *.log files in test directory "dir" should be all sorted.
4 Find recursively in a given directory all the symbolic links, and report those that point to files/directories that no longer exist. Use operator -L to test if a path is a symbolic link, and operator -e to test if it exists (will return false if the target to which the link points does not exist) find, if
5 Write a script that receives dangerous program names as command line arguments. The script will monitor all the processes in the system, and whenever a program known to be dangerous is run, the script will kill it and display a message. while, ps, sleep, grep, kill, true 

    

    

        6
        Find recursively in a directory, all the files that
            have write permissions for everyone. Display their names, and the permissions before and after
            removing the write permission for everybody. You
            will need to use chmod's symbolic permissions mode, instead
            of the octal mode we have used in class. The the chmod manual
            for details.
        
        find, chmod, ls
        
-rwxrwxrwx dir/d/c/b/15.c
-rwxrwxr-x dir/d/c/b/15.c
-rwxr---w- dir/d/b/6.txt
-rwxr----- dir/d/b/6.txt
-rwx-w-rw- dir/c/b/9.sh
-rwx-w-r-- dir/c/b/9.sh

    

    

        7
        Consider a file containing a username on each
            line. Generate a comma-separated string with email addresses
            of the users that exist. The email address will be obtained
            by appending "@scs.ubbcluj.ro" at the end of each username.
            Make sure the generated string does NOT end in a comma.
        
        for, finger, grep, sed
        Input file 
a
b
c
 should result in output 
a@scs.ubbcluj.ro,b@scs.ubbcluj.ro,c@scs.ubbcluj.ro

    

    

        8
        Display all the mounted file systems who are either smaller than
            than 1GB or have less than 20% free space.
        
        df, awk, sed
        
/dev
/run
/dev/shm
/run/lock
/sys/fs/cgroup
/run/user/1000
/home/rares/osvm

    

    

        9
        Write a script that finds in a given directory hierarchy, all
            duplicate files and displays their paths. Hint: use checksums
            to detect whether two files are identical.
        
        find, md5sum, for, sed, awk, sort, uniq, head, tail
        

    

    

        10
        Display the session count and full names of all the users who logged into the
            system this month, sorting the output by the session
            count in descending order. Use the -s and/or -t options of command last
            to get this month's sessions, and the command date to
            generate the required timestamp in the expected format.
        
        date, last, grep, sort, uniq