Command Line Crash Course for Beginners

Lencia Beltran Open Science Project Coordinator
Office: 4416, Sorrells Library
lbeltran@andrew.cmu.edu

Windows:
1. Click the Windows icon to bring up your start menu. Type cmd into the search box.
2. Select the command prompt entry and click open.
3. Occasionally, you must select the run as administrator option to use higher-level system commands.
Mac:
1. click command and space bar then type terminal
2. click spotlight search icon (magnifying glass), then type terminal

pwd AKA print working directory
ls AKA print a list of items in your working directory (including different options);
1. ls -a (show all)
2. ls -F(add trailing /) / means it’s a directory and * means it’s a program
3. ls -l
4. ls -Fa
5. ls -laF
Navigating up files
1. cd
Navigating down files
1. cd.. (move back a directory)
  - To view files in higher level directories can also do ls ../ which will go back 2 levels and show your root/home directory (lbeltran) or go back 1 level ls ../../ to see files in your Desktop directory
2. cd ~ takes you straight to your root/home directory
  - Question! What is the different between cd.. and cd~ ?
Relative and absolute paths
1. A relative path always starts with / and gives the full address from the home directory (think of this as getting GPS coordinates, no matter where you are it will tell you where something is and how to get there)
2. An abosolute path will only give the address from the working directory, and does not start with a / (analogous to getting directions from someone on the street in real time)

Navigate to their desktop & create 3 new directories. The first directory will be on your desktop.
- mkdir name1
Navigate into doing cd name1 and then make 2 directories. We can do this quickly by listing both names as shown below. Note, be careful you dont add a space in a name because that will make two directories!!
- mkdir name2 name3
Navitgate into name2 directory
- and create a nano text file

Open up the nano text editor or your favorite text editor. Note, this may be different for
- nano
Copy and paste text
- access help in nano by
  - (control G)
Save the text (control C) and name the file practicetext_1
Exit the editor (control X)

To repeat the most recent/recently command run, use the up arrow
The down arrow will take you forward in your in the command history
- Ctrl+C will cancel the command you are writing, and give you a fresh prompt.
- Ctrl+R will do a reverse-search through your command history. This is very useful.
- Ctrl+L or the clear command will clear your screen.
To review recent command history
- history
To rerun a specific command in your command history
- add a ! in front of the number
  - e.g., !22

Make a copy of the text file
- cp practicetext_1 practicetext_1_copy
- check that a copy of our text data was made ls -F
Make a backup directory to store the copy of the text data and any copies
- mkdir backup
- Note: make sure you are creating directories in the correct working directory (i.e., make sure you are in the right working directory)
Move your copy of the text data into the backup directory
- mv practicetext_1_copy backup
You can either navigate to backup and type ls OR type ls backup
Rename the copy of the text
- mv also let’s you rename files
  - mv practicetext_1_copy practicetext_1_backup

Remove the backup copy of the text file
- rm practicetext_1_backup
Remove all of the directories under name1
- rm -r name1
  - A recursive flag -r will need to be added to tell rm to remove a directory
- Note, remove will permanently delete a file but also any content in a directory (i.e., not only the directory name1 but will also remove everything in the directory)