4. Linux Commands and Exercise

Command Action Accomplished

• pwd Display the complete path of the directory you are currently positioned in

• ls List the contents of the directory; often used with the –a (all) and –l (long listing) options

• mkdir <dir_name> Create a subdirectory under the current working directory

• cd Change directory to the one whose location is specified, or to home directory, if nothing is mentioned

• clear Clear screen

• date Displays the current date and time

• who Displays the list of all users logged in

• who am i Displays your own username and details

• cal Calendar – also takes arguments

• man <command> Displays the user manual entry for the command mentioned

• cat If used with filename(s), displays the contents of the file(s); also used to create new files

• logout Logs you out of the system

• echo Displays whatever follows to the standard output (screen)

• cp <source> <dest> Copies the source file into destination (destination can be file or directory)

• mv <source> <dest> Rename the source file as destination

• rm <file> Remove the file(s) given as arguments; can also be used with the –rf option to remove a directory that is non-empty

• bc Starts the calculator programme

• wc Displays word, character and line count of the file (or standard input)

• head Displays the first few lines of a file

• tail Displays the last few lines of a file

• grep Search for the given pattern and print those lines that have that pattern

• tree Print the file structure of the given directory (or current directory)

• chmod Change permissions of a file

1. Make a directory called assign1 under your home directory.

[rkmishra@linuxbpdc1]$ mkdir assign1

2. Change to this directory.

[rkmishra@linuxbpdc1]$ cd assign1

3. Make three empty files: file1 file2 and file3.

[rkmishra@linuxbpdc1]$ vi file1

[rkmishra@linuxbpdc1]$ vi file2

[rkmishra@linuxbpdc1]$ vi file3

4. Change back to your home directory.

[rkmishra@linuxbpdc1]$ cd

Or [rkmishra@linuxbpdc1 ]$ cd ~

5. Store the list of all the directories (long listing) in a file called dirfile.

[rkmishra@linuxbpdc1]$ ls –al > dirfile

6. Display the contents of dirfile on the screen.

[rkmishra@linuxbpdc1]$ cat dirfile

7. Display on the screen the current time in the format hh:mm:ss.

[rkmishra@linuxbpdc1]$ date +"%I:%M:%S"

8. Copy /home/rkmishra/FILE1.txt as file1 under the directory assign1.

[rkmishra@linuxbpdc1]$ cp /home/rkmishra/FILE1.txt assign1/file1.txt

9. Make assign1 as your current directory.

[rkmishra@linuxbpdc1]$ cd assign1

10. Execute a sequence of commands so that file2 contains the first five lines and the last ten lines of file1. (you can use more than one command for this task).

[rkmishra@linuxbpdc1]$ head -n 5 FILE1.txt | tail -n 10 FILE1.txt >FILE2.txt

11. Count the number of times the word program appears in file1. (Hint: -o option)

[rkmishra@linuxbpdc1]$ grep -o 'program' FILE1.txt |wc -l

12. Change access privileges of file2 such that none except you can modify it but every user (including you) can read and execute it.

[rkmishra@linuxbpdc1]$ chmod 755 FILE2.txt

13. Print only the total number of lines of file1 and file2.

[rkmishra@linuxbpdc1]$ cat FILE1.txt FILE2.txt |wc -l

14. Print the current file structure of your home directory.

[rkmishra@linuxbpdc1]$ tree

15. Open file3 using vi editor and add the following line of text to it: This is file3!

16. Save and exit editing file3.

17. Append the contents of file2 to file3.

[rkmishra@linuxbpdc1]$ cat FILE2.txt >> FILE3.txt

18. Open file3 using vi editor again, and insert the following line after the first line: (25 stars)

*************************

19. Insert such a line after the last line of file3, just by using vi commands (that is, do not type out the line again).

20. Save the modified file into another file named file4.

:w FILE4.txt

21. Now, count the number of characters in file4, without exiting vi editor.

[rkmishra@linuxbpdc1]$ wc FILE4.txt -c

22. Exit vi editor, so that none of these changes you made is recorded in file3.

:q!