UNIX COMMANDS

• LEVEL - I

1. List all the files and subdirectories of the directory /bin = cd bin ls bin
2. List all the files including hidden files in your current directory = ls -a
3. List all the files starting with letter 'r' in your current directory = ls r*
4. List all the files having three characters in their names from your current directory. = ls ???
5. List all the files with extension .doc in your current directory = ls *.doc
6. List all the files having the first letter of their name within the range 'l' to , 's'  from your current directory =  ls [l-s]*
7. Create a file text1 and read its input from keyboard = cat > text1
8. Copy contents of file text1 to another file text2 = cp text1 text2
9. Append the contents of file text2 to file text1 = cat >> text1 text2
10. Count the number of files in the current directory = ls|wc -w
11. Display the output of command ls -l to a file and on the output screen = ls -l|cat > text3 or ls -l|cat>>text2
12. From file text1 print all lines starting from 10th line = tail +10 text1
13. Find the number of users currently logged on to the system = who|wc -l
14. Delete all the files with their names starting with "tmp" = rm tmp*

• LEVEL - II

1. Create a file FILE2 with some text in it. Increase the no. of hard links to the file FILE2 to 3 and check the inode number and link count for those names = ls -l FILE2 Fl1 Fl2|cut -d " " -f3,10
2. Using one single command, display the output of "who" and "pwd" commands = who;pwd
3. Display today's date = echo "Today is $(date+%a) $(date+%d) $(date+%h) $ (date+%y) "
4. Display the text message on monitor screen "We are done!!!" = echo "We are done!!!"
5. Display the message on monitor screen "The long listing of my home dir ----- is -----" = 'the long listing of my home dir '; pwd; echo ' is ';ls -l

• LEVEL - III

1. List only the directories in your current directory = find -type d|nl
2. Display the name and count of the directories in the current directory = find -type d -print; find -type d|wc -l
3. Find out whether the users with a pattern "itp9" in their names have logged in = who|cut -d " " -f1|fgrep itp9
4. Find out whether a particular user "itp9" has logged in
•  n=`who|cut -d " " -f1|fgrep ncs|wc-l`           if test $n -ne 0
            then
                  echo -e "no"
            else
                  echo -e "yes"
           fi 
5. Assign a value "Black" to var1 and then display the following message on the terminal using this variable "Sirius Black is a true marauder."
• Set var1 Black
• echo "Sirius $var1 is a true marauder."
6. Create the file employee.txt having ":" separated fields.  The fields of record are : enumber, ename, eposition, esal, edoj, edept. Now answer the following.

1. List all the employees along with a row number = cat employee.txt|cut -d ":" -f2|nl
2. Sort the files as per names = cat employee.txt|sort -t ":" +1 -2
3. List top three salaried employees = cat employee.txt|sort -r -t ":" +3 -4|head -3
4. Rmove duplicate record from the file = cat employee.txt|unique
5. List dept. no along with no. of emplooyees working in each dept = cat employee.txt|cut -d ":" -f6, 1|unique
6. Sort the file in descending order of salary = cat employee.txt|sort -r -t ":" +3 -4

• LEVEL - IV

1. Accept a file name and a number (x). Display x lines from the top of the file. Check if the file exists and is readable. The value of x should not exceed the total no. of lines in the files. Display suitable messages in case an error is encountered.

             echo 'Enter the file name'
             read file
             if test -e file
             then
                    echo 'File exists.'
                    if test -r file
                            echo 'File is readable'
                            echo 'Enter the line no.'
                            read n
                            x=`wc.. -l $file|cut -d " " -f1`
                            if test $n -lc $x
                            then
                                  head -$n $file
                           else
                                 echo 'The value exceeds total no of lines.'
                           fi
                    else
                          echo 'File is not readable'
                    fi
               else
                    echo 'File doesn't exist'
               fi