the shell
- a command line interface for running programs
- it runs programs for you
- it receives the input => run programs => send the output
- the vast majority of web servers in the wild run on linux, and the shell is a vital tool for deployment and remote administration on linux servers
- fast and flexibile
- command line interpreter
- to interact with the shell we use a program called the terminal
- A Unix shell is both a command interpreter and a programming language.
- it's more than a user interface, it's also a programming language
scripts
files containing the shell commands are called shell scripts
variables
shell variables
- internals to the shell program itself
- e.g: LINES and COLUMNS
environment variables
- shared with programs that you run from within the shell
- e.g: PATH and PWD
- PATH environment variable: tells your system where your program files are
terminal (terminal emulator) VS TTY (teletype) VS console VS shell VS prompt VS command line VS CLI (command line interface) VS GUI (graphical user interface)
- terminal: tty = input/output environment
- console: the physical keyboard and monitor attached to a machine
- shell: command line interpreter
- prompt: the part before the command line
- command line: the line we are typing on
- command line interface: an interface that you can interact with it by typing
- graphical user interface: an interface that you can interact with by the mouse and keyboard
terminal
- a program that draws text on a window and lets you type things on the keyboard
- called terminal emulator
- display output to the screen
- accepts input from the keyboard
- doesn't know what to do with the input, so it needs another program that knows what to do which is the shell
- when you type things in, the terminal sends what you type to the shell
- when you press enter
- the shell interprets what you wrote as a command
- figure out what program you want to run
- runs it
- send the output back to the terminal
- you can use the terminal without the shell and using the python interpreter instead
- programs you can use inside the terminal
- shell
- python interpreter
- you can use the shell without the terminal by using shell scripting
- text input/output environment
CLI VS GUI
benefits of CLI
- use less system Resources
- more
types of the shell
- bash
- zsh
- sh
- fish
- cmd
- powershell
- ksh
- csh
- tcsh
the linux shell
the Linux shell comes with a long list of commands that can be composed to automate any task imaginable.
This ability to build larger programs from smaller ones is what gives the command line its power and flexibility.
notes
- how to write clean code
- A good command line interface is the Linux shell
- the javascript console is a CLI for the browser, and the shell is the CLI for the whole computer in general
- the bash shell is the most popular UNIX-style shell
- you can use the shell without the terminal
- by writing shell commands into a file and arrange for your computer to run the shell program on that file (shell scripting)
- you can use the terminal without the shell
- by making it run the python interpreter for example
- you can interact with a system using either
- GUI
- CLI
- a flag is used to alter how a program functions
- Flags can be used to alter how a program functions and/or what is displayed.
- a diff and a patch refer to the same thing