Unix Essentials!

1. pwd (print working directory)

2. ls (list)

   #without argument curr directory
   ls
   #with argument
   ls DIRECTORY
   

3. cd (change directory)

   #without argument home directory
   cd
   #with argument
   cd DIRECTORY
   # back
   cd ..
   

4. mv (move or rename)

   #move
   mv FILE_OR_DIRECTORY_NAME  NEW_DIRECTORY
   #rename
   mv FILE_OR_DIRECTORY_NAME  NEW_FILE_OR_DIRECTORY_NAME
   

5. cp (copy)

   #same directory
   cp ORIGINAL_FILENAME  NEW_FILENAME
   #another directory
   cp ORIGINAL_FILENAME  DIRECTORY
   #copy directory
   cp -r ORIGINAL_DIRECTORY  NEW_DIRECTORY
   

6. cat (concatenate - prints the contents of a file)

   cat FILENAME
   

7. rm (remove)

   #delete
   rm FILENAME
   #delete all
   rm  *
   #non-empty directory
   rm -r DIRECTORY_NAME
   

8. mkdir (make directory)

   mkdir  DIRECTORY_NAME
   

9. rmdir (remove directory)

   rmdir  DIRECTORY_NAME
   

10. print n lines

    #print n lines
    head -n 2 FILENAME
    tail -n 2 FILENAME
    #combine
    head -n 20 FILENAME | tail -n 5
    #watch the file update
    tail -f FILENAME
    

11. show history

    #show history
    history
    

12. clear screen

    #clear screen
    clear
    

13. install / update packages

    #install
    sudo apt-get install packagename
    #update
    sudo apt-get update
    

14. grep <str> <files> (Find which files contain a certain word)

    grep "some word" *	
    

15. chmod <opt> <file> (Change file permission)

    #Change file permissions read only
    chmod 644 *.html 
    

16. ps <opt> (List running process)

    #List all running processes by #ID
    ps aux 
    #List process #ID's running by dhyatt
    ps aux | grep USERNAME	
    

17. kill <opt> <ID> (kill a process)

    #Kill process with ID #8453
    kill -9 8453	
    

18. gzip <file>

    #Compress file
    gzip bigfile 
    #Uncompress file
    gunzip bigfile.gz	
    

19. awk (Pattern search, replace and more)

    #Print the lines which matches with the given pattern.
    awk '/someword/ {print}' FILENAME
    #Print 1st and 4th column
    awk '{print $1,$4}' FILENAME
    #Replace comma by null in 3rd column
    awk '{ gsub(",","",$3); print $3 }' FILENAME
    

20. diff (Compare files)

    diff FILENAME1 FILENAME2
    

21. at (Scheduling a job)

    #Schedule a job
    echo "sh backup.sh" | at 9:00 AM
    echo "sh backup.sh" | at now + 30 minutes
    #List the scheduled jobs using atq
    atq
    #Remove scheduled job using atrm
    atrm 3
    

22. more / less (pagination tool for viewing text files)

    cat FILENAME | more
    

23. date (print current date)

24. & (the & informs the shell to put the command in the background)

    sh shell_script.sh &
    

25. nohup (prevents the command from being aborted automatically when you log out or exit the shell)

    nohup sh shell_script.sh -y &
    

26. Download a file with wget

    wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh
    

27. Download a file with curl

    curl -fsSL -o Miniconda3-latest-MacOSX-x86_64.sh https://repo.anaconda.com/miniconda/Miniconda3-latest-MacOSX-x86_64.sh