Bash Commands Review

## Terminal, Shell, and Command Line Basics - **Command line**: A text interface where users type commands. - **Terminal**: The application that provides access to the command line. - **Terminal emulator**: Adds extra features to a terminal. - **Shell**: Interprets the commands entered into the terminal (e.g., Bash). - **PowerShell / Command Prompt / Microsoft Terminal**: Options for accessing the command line on Windows. - **Terminal (macOS)**: Built-in option on macOS, with third-party alternatives like iTerm or Ghostty. - **Terminal (Linux)**: Options vary by distribution, with many third-party emulators like kitty. - **Terminology**: Though "terminal," "shell," and "command line" are often used interchangeably, they have specific meanings. ## Command Line Shortcuts - <kbd>Up Arrow</kbd>/<kbd>Down Arrow</kbd>: Cycle through previous/next commands in history. - <kbd>Tab</kbd>: Autocomplete commands. - <kbd>Control</kbd> + <kbd>L</kbd> (Linux/macOS) or typing `cls` (Windows): Clear the terminal screen. - <kbd>Control</kbd> + <kbd>C</kbd>: Interrupt a running command (also used for copying in PowerShell if text is selected). - <kbd>Control</kbd> + <kbd>Z</kbd> (Linux/macOS only): Suspend a task to the background; use `fg` to resume it. - **`!!`**: Instantly rerun the last executed command. ## Bash Basics - **Bash** (Bourne Again Shell): Widely used Unix-like shell. Key commands: - **`pwd`**: Show the current directory. - **`cd`**: Change directories. - **`..`** refers to the parent directory (one level up). - **`.`** refers to the current directory. - **`ls`**: List files and folders. - **`-a`**: Show all files, including hidden files. - **`-l`**: Show detailed information about files. - **`less`**: View file contents one page at a time with navigation options, including scrolling backward and searching. - **`more`**: Display file contents one screen at a time, with limited backward scrolling and basic navigation. - **`cat`**: Show the entire file content at once without scrolling or navigation, useful for smaller files. - **`mkdir`**: Create a new directory. - **`rmdir`**: Remove an empty directory. - **`touch`**: Create a new file. - **`mv`**: Move or rename files. - Rename: `mv oldname.txt newname.txt` - Move: `mv filename.txt /path/to/target/` - **`cp`**: Copy files. - **`-r`**: Recursively copy directories and their contents. - **`rm`**: Delete files. - **`-r`**: Recursively delete directories and their contents. - **`echo`**: Display a line of text or a variable's value. - Use `>` to overwrite the existing content in a file. (e.g., `echo "text" > file.txt`) - Use `>>` to append output to a file **without overwriting existing content** (e.g., `echo "text" >> file.txt`). - **`exit`**: Exit the terminal session. - **`clear`**: Clear the terminal screen. - **`find`**: Search for files and directories. - **`-name`**: Search for files by name pattern (e.g., `find . -name "*.txt"`). - Use **`man`** followed by a command (e.g., `man ls`) to access detailed manual/help pages. ## Command Options and Flags - **Options** or **flags**: Modify a command's behavior and are usually prefixed with hyphens: - **Long form (two hyphens)**: - Example: `--help`, `--version` - Values are attached using an equals sign, e.g., `--width=50`. - **Short form (one hyphen)**: - Example: `-a`, `-l` - Values are passed with a space, e.g., `-w 50`. - Multiple short options can be chained together, e.g., `ls -alh`. - **`--help`**: You can always use a command with this flag to understand the available options for any command.