6 min to read

Command Line Every Programmer Must Know

Mastering the command line is a must for every programmer.

Interacting with a computer through a command-line interface (CLI) is a powerful technique. Mastering the command line can greatly improve your productivity during development. The best way to do this is to keep a list of selected commands ready for a quick glance whenever you get stuck.

Below is a curated list of the most fundamental commands. Would suggest to bookmark this post.

STARTER

• Find out the language of the terminal (zsh/bash/sh): echo $0
• Print the current path: echo $PATH
• Read manual of a command: man <cmd> ([ENTER] to scroll, q to quit)
• Add sudo automatically to the last command: sudo !!
• Give your own name to a command: alias cls=clear (Alias for a sequence of command to be wrapped in quotes. To make alias permanent, add the commands in .zshrc)
• Change the password of a user: sudo passwd <username>
• Ping the server: ping <URL>

SYSTEM INFO AND SETUP

• Linux System Information: uname -a (use w to see current logged-in users)
• Real-time status of system processes: top (you can use ps also for listing current processes)
• Kill a process by specifying its PID: kill
• Exit (terminate) any current process and start a new line: ^c (^ = [CTRL])
• Manage System Settings: sudo systemsetup
• Report System Hardware and Software Configurations: system_profiler
• System Security Frameworks: security
• Manage system configuration parameters: scutil --help (Ex. scutil --get HostName, sudo scutil --set HostName <Host_Name>)
• Set an environment variable: env (you can also use export)

WORKING WITH DIRECTORIES

• Print the working directory: pwd
• Go back to a directory: cd ..
• Go two directories back: cd ../..
• Go to Root directory: cd /
• Go to Home directory: cd [ENTER]
• Create a directory: mkdir <dir_name>
• Create multiple directories: mkdir <dir1> <dir2> <dirN>
• Remove dir: rm -rf <dir_name> (r - recursive, f - force)

WORKING WITH FILES

• View files in directory view with details: ls -1 (use -lt or add -t to sort, -a to list hidden files)
• View files with a specific file extension: ls *<.extn>
• List the files in a specific directory: ls <dir_name>
• Create a file: touch <file_name>
• Create a file in a directory using echo: echo "<text>" > <file_name>
• Copy file: cp <copy_file> <copied_file>
• Rename file: mv <file_name> <new_name>
• Move file: mv <file_name> <dir_path>
• Remote file copy: rsync SOURCE DESTINATION
• Read a file: cat <file_name> | less (Lists the contents of files to the terminal window, faster than Open. Less allows to use up & down keys. Type q to quit from less.)
• Print first few lines of a file: head example.txt (‘use -n , default is 10. use `tail` for printing last lines.)
• Open a file: open <file_path>
• Remove file: rm <fine_name> (this will remove file not dir)
• Securely remove files or directories: srm <file_name>
• Write to a file: echo "<text>" >> <file_name> (use > to rewrite the text)
• Search: grep <search_string> <file_name> (grep can search in multiple files, use wildcard *. instead file name.)
• Print text of multiple files together: cat <file1> <file2>
• Concatenate content of multiple files: cat <file1> <file2> > <file3>
• Merge two files with output to outfile: sdiff -o outfile from-file to-file
• To set file permissions: chmod -R 765 example.txt (Digits seq for Owner, Groups, & Others. Permissions: 0-No permission; 1-Execute(x); 2-Write(w); 3-Write and execute; 4-Read(r); 5-Read and execute; 6-Read and write; 7-Read, write and execute
• Compress a file: gzip -k example.txt
• Display file details: stat <file_name>
• List the metadata attributes for a specified file: mdls <file_name>
• Download file from internet: wget <URL>
• Unzip file: unzip <file_name>
• Edit a file: nano <file_name> (nano is a text editor)

VIRTUAL ENV

• Create a new virtual environment: python -m venv <dir_name>
• Goto <dir_name>/bin and activate: source activate (This will prepend the path to “venv” at the beginning of the $PATH variable)
• Exit the virtual environment: deactivate

PYTHON

• Open Python terminal: python
• Execute a command: python -c "print('Real Python')"
• Exit Python terminal: >>> exit() (or \[CRTL]D)
• Map Python Version (Mac ZSH): echo "alias python=/usr/local/bin/python3.7" >> ~/.zshrc

PIP

• Pip packages: https://pypi.org/
• Pip install package: pip install <package-name>
• Install specific development version from Github: python3 -m pip install git+<git_URL>
• Pip upgrade package: pip install --upgrade <package-name>
• Force install a version if you’ve already installed: python3 -m pip install --force-reinstall git+<git_URL>
• Pip uninstall package: pip uninstall <package-name>
• Pip install by preventing the cached installation: pip install <pachage_name> --no-cache-dir
• List pip packages installed on the env: pip list
• Generate a requirements file: pip freeze > requirements.txt
• Install dependencies from a requirements file: pip install -r requirements.txt

JUYPTER NOTEBOOK (Optional)

• Installation: https://jupyter.org/install
• Start Jupyter Notebook: jupyter notebook
• Browse at http://localhost:8888/

RASA (Optional)

• Installation: https://rasa.com/docs/rasa/user-guide/installation/
• Create new project: rasa init --no-prompt
• Train model: rasa train
• Run action server: python -m rasa_sdk --actions actions
• Run bot locally: rasa shell
• Run interactive bot: rasa interactive -m models --endpoint endpoints.yml
• Run the bot on external channels: rasa run -p 80
• Use Rasa X features for testing and interactive learning: rasa x

JEKYLL (Optional)

• Installion: https://jekyllrb.com/docs/
• Create a new Jekyll site at ./myblog: jekyll new myblog
• Build the site and make it available on a local server: bundle exec jekyll serve
• Browse at http://localhost:4000

ULTIMATE TRICKS

• Youtube video download: youtube-dl <URL> (1. install youtube-dl. use -F to list available formats, -f <format_code1>+<format_code..n> to download specific formats.)
• Download file from internet: curl -s <URL> > <file_name> (-s to see the download progress, you can use -o (output) option for saving the file)
• Capture an image of the whole or part of the screen: screencapture -i -p (for other options, refer man screencapture)
• Convert text to audible speech: cat myfile.txt | say (for other options, refer man say)
• Prevent the system from sleeping: caffeinate -u -t 3600 (caffeinate for 1 hour)

Not satisfied, need a more comprehensive list? Check this.