Basic Command Line Codes.md

Basic-Command-Line

• A line where you type commands
• Other terms:
  • CLI (Command Line Interface)
  • Console/terminal
  • Shell
• Advantages: Simple(nearly always work even if computer breaks other way), fast and efficient if you know the commands, easy to program (in comparison to GUI)
• Disadvantages: Have to memorize command.
• Common elements of the console prompt statement

  • shows username (who is using this)

  • host name (what computer you are on)

  • working directory (where on the computer are we)

  • Command prompt where we type to give input starts with $ or > .

  • Command prompt looks like this:

    [dg663@cbsurobbins Desktop]$

• Very case sensitive

Notes on basic command line for Terminal.

First never run a command which you don't understand For eg. sudo rm -rf / will remove everything (though many idiots on internet provoke this as a fun.)

Apple MacOS offers native Terminal app that features access to the command-line interface. Many Mac terminal commands are similar to Linux commands.

Terminal_Linux Command Line Codes: Type of command, its code, function of the code and examples attached herewith.

1. Current Directory or Present working directory: pwd

• Function of the code: If you want to find out which directory you are in.
• Example. pwd
• Result: in my case "/Users/dg663"

2. Change Directory: cd

• Function of the code: The cd command will change the directory you’re currently working within Terminal to execute other commands on a different directory.
• Example: cd “path/to/directory/”
• Like: cd Desktop
• Result: Changed to Desktop directory

3. Listing Directory: ls

• Function of the code: Use ls command after navigating into a directory using the cd command to view the contents inside of the current directory.
• Example: ls and get everthing inside that directory.
• Also, Use the argument -l command with ls to get even more information about each of the files.
• Example: ls -l
• Also, to list by specific sorting: ls -tor
• ls -tor means ls command or list and sort files by modification time(t), displays output (o) in long format and reverses the files first (r). So, ls -tor will list files in reverse order of modification time, in a detailed format without the group information.

4. Open Files: open or cat

• Function of the code: When browsing a directory, you may encounter a file that you wish to open on your Mac. That’s where the open command comes in.
• Example: open “filename” or cat filename
• i.e. like open Dinesh
• Then a folder named Dinesh will open up in the new desktop window. Edit file:

5. Copy a file to another directory: cp

• Function of the code: The cp command facilitates copying a file from one location to another or making a copy of the same file with a new name.
• Example: cp “filename” “newfilename with directory”
• i.e. cp Disease.docx /Users/dg663/Documents/Disease.docx
• By doing so, I copied that file named Disease.docx into documents folder.

8. Move a file: mv

• Function of the code: When you don’t want to copy a file, but instead move it, use the same format of the cp command, but instead replace cp with mv.
• Example: mv “filename” “path/to/new/file/location”
• i.e. mv Disease.docx /Users/dg663 (moved to dg663 folder)

9. Create a text file: touch

• Function of the code: The touch command allows you to create any type of file, but it’s blank.
• After you create the blank file, you can open it in a text editor by typing open [filename].
• Example: touch myfile.txt , also you can create other types(doc, csv) by typing touch myfile.doc or touch myfile.csv
• Then open myfile.txt to open it.

10. Create a directory or folder: mkdir

• Function of the code: The mkdir command will allow you to create a directory (folder) from within the CLI.
• When you need a place to store new files, just use this command to add a new directory in the current working directory, or specify a full path to the location where you want the new directory to be placed.
• Example: mkdir “path/to/new/directory”
• i.e. mkdir /Users/dg663/new so here a new folder created inside dg663

11. Rename folder: mv

• Function of the code: When you’ve created a folder that has the wrong name, you can easily use the mv command to rename it.
• Example. mv "oldfilename" "newfilename"
• i.e. mv myfile.txt file.txt

12. Remove an empty directory: rmdir

• Function of the code: If you want to remove a directory altogether, use the rmdir command followed by the path to the directory.
• Example: rmdir “path/to/directory”
• i.e rmdir /Users/dg663/new now removes that new folder.

13. Remove nested directories or folder: rm -R command

• Function of the code: When you want to remove an entire directory that might contain other directories or files, then the rm -R command is where you will turn.
• This command is irreversible, unlike deleting files in the Finder and being able to restore them from the Trash.
• When this command is executed, all files and directories inside of the path you specify will be deleted immediately.
• Example: rm -R “/path/to/root/directory”
• i.e. like mkdir /Users/dg663/test created a test directory or folder
• Then this one removes it. rm -R /Users/dg663/test

Note: Here rmdir removes only empty directory but rm -R removes both empty and non empty

12. Execute commands with superuser privileges: sudo command

• Function of the code: sudo which stands for "superuser do" is a command that allows a permitted user to execute a command as the superuser or another user. i.e. Allows you to access your user privileges while executing the command to administrator privileges.
• This is required for some commands to run — for instance, removing a file that is owned by another user.
• When you run this command, you will see a password field appear in Terminal where you will need to type your user account password to finish the command execution.
• Your Mac has security baked in at its core, which is why when typing a password, the command line hides the characters typed for security practices.
• Remember to never type your password into a field that you did not request!
• Example: sudo “command” i.e like sudo open myfile.txt
• Then, asked for password and you won't know if you have typed or not, it just looks empty.
• But keep on typing the correct password for your user account.
• If you are using computer from your school and you don't have full administration control, you might have to allow it manually like by using "self service control" software.
• You can install it by requesting your IT guys or even you might be able to download on your own.

13. List all actively running computer processes: top

• Function of the code: With top command, you can see the stats of your system updated in Terminal’s window, such as the memory, disk utilization and so on.
• You’ll also see a running list of the top apps using the CPU, including their state, ports used, memory per app and more, without needing to open the Activity Monitor app on your Mac. Example: top Note that: This command will execute until you close Terminal’s window or press Control + C to return execution back to the CLI.

14. Quit sub-screen of perpetuity and return to Terminal: q

• Function of the code: For commands that run in perpetuity when executed, you can end execution of the process by pressing the q key on your keyboard.
• Alternatively, you can press Control + C.
• Example: q or Ctrl C Perpetuity refers to never ending process like top function above

15. Clear terminal screen: clear

• Function of the code: It clear out all commands and returns a clean slate to work from
• Example: clear

16. Copy contents of a folder to a new folder: ditto

• Function of the code: The ditto command will execute a copy of all of the contents of one folder into another folder you specify.
• This is great for when you need to start a new project and use an older project as a base or if you just need to copy files in a folder from your computer to an external drive.
• Add a -V, as in the example below, to get verbose output for each file copied.
• Example: ditto -V MyFolder MyNewFolder i.e ditto newfolder Dinesh (here newfolder contain a subfolder which was copied to Dinesh using this command) Note: You can use -V to get verbose output and you can use it without -V too.

17. Get description of a command: whatis

• Function of the code: If you are unsure or do not know what some command does, you can use this to get a short description of a command.
• Example: whatis ditto then the result will be different things that ditto does. Don't worry about "Not a directory" sign.

18. Manual of the command: man

• Function of the code: If the description is not enough or you want to know more about the command, the good news is that most of the command are shipped with a manual.
• You can use man command to know more about the command and get a manual of that command.
• Example: man ditto . The result consists of description with the manual page including but not limited to Name, synopsis, description and so on.

19. Exit Command: exit

• Function of the code: It closes the current session in Terminal. Especially used during remote control.
• If you are directly using in your computer on site, you can just close the window as well.
• Example: exit
• The result will be saving session.... [Process completed]

20. Force shutdown apps: killall

• Function of the code: If you want to forcefully quit some app, you can use this function. This can be really important sometime.
• Example: Killall Terminal
• The result is that the terminal window will be closed.

21. Github Codes: 21.1. Git Clone: Clone a file or folder

• Function of the code: If you want to clone a file instead of downloading a zipfile because cloning can help you to keep track of files and can use git push or pull to update the folder.
• Example: git clone (paste ssh or url)
• The result is that the folder will be downloaded.

21.2. Cloning the Repository: To clone the repository, use the following command:

• git clone [email protected]:dineshghimire01/REU-Summer-2024-Cornell.git

21.3. Keeping the Cloned Repository in Sync To keep the cloned repository in sync with the original repository, follow these steps:

• Fetch the latest changes from the remote repository:
• git fetch origin

21.4. Switch to the main branch:

• git checkout main

21.5. Pull the latest changes from the remote repository:

• git pull

21.6. Working on the main Branch

• To work on the main branch and commit your changes, follow these steps:
• Check the modified files:
• git status

21.7. Stage the modified files:

• git add <file_name>

Or, to stage all modified files (not recommended):

• git add .

21.8. Commit the changes with a descriptive message:

• git commit -m "Your commit message here"

21.9. Push the changes to the remote repository:

• git push

or

• git push origin

21.10. Bonus Git Commands 21.10.1 **Check the status of the current branch:

• git status

21.10.2 View changes made to files:

• git diff

or

• git diff <file_name>

21.10.3 Create a new branch and push it to the remote repository:

• git checkout -b <branch_name>
• git push -u origin <branch_name>

21.10.4 Switch to an existing branch:

• git checkout <branch_name>

21.10.5 List all branches:

• git branch

22. Few more:

• Search_term : To check if the file is present in the directory:
  • if you are already in the directory: grep -r
  • if you are not: grep -r "search_term" /path/to/directory
  • Here, grep means Global Regular Expression Print which is used to search for specific patterns within files by using regular experessions i.e. this means globally search for a regular expression and print
  • and r means recursive : option tells grep to search through all files in a specified directory and its subdirectories