Overview
bash is an enhanced version of the Bourne Shell (sh), combining interactive shell features with powerful scripting capabilities. It offers convenient features such as customizable prompts, command completion, and history search, making it essential for writing complex automation scripts.
Key Features
Core functionalities provided by bash.
- Command history and editing
- Tab completion (for files, commands, variables, etc.)
- User customization via aliases and functions
- Job control (managing background/foreground processes)
- Robust shell scripting support
- Environment and shell variable management
Key Options
Major options that can be used when running the bash command itself. These control how scripts are executed or how the shell behaves.
Execution Modes
Script Debugging
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Usage Examples
Examples of running the bash shell in various ways or processing scripts.
Start a basic interactive shell
bashStarts a new bash shell session.
Execute a command string
bash -c "echo 'Current directory: $(pwd)'"Uses bash to execute a specific command string and then exit.
Execute a script file
bash my_script.shRuns a specified bash script file.
Start a login shell
bash --loginStarts a bash shell that loads initialization files as if it were a login shell.
Execute script in debugging mode
bash -x my_script.shTraces and prints each command as the script executes.
Execute script from standard input
echo "ls -l" | bash -sAllows the bash shell to execute commands passed via a pipe.
Tips & Considerations
Tips for making bash usage more efficient and points to consider when writing scripts.
Key Configuration Files
Major configuration files used to customize the behavior of the bash shell.
- ~/.bashrc: Executed when an interactive shell starts. Used for defining aliases, functions, prompt settings, etc.
- ~/.bash_profile: Executed when a login shell starts. Used for setting environment variables, calling other initialization scripts, etc.
- /etc/profile: System-wide login shell configuration file. Contains settings applied to all users' login shells.
Scripting Best Practices
Recommendations for writing robust and efficient bash scripts.
- Start scripts with `#!/bin/bash` (shebang) to explicitly specify bash as the interpreter.
- Always quote variables to prevent issues with spaces or special characters (e.g., `echo "$VAR"`).
- Use `set -e` to exit immediately if a command exits with a non-zero status, and `set -u` to treat unset variables as an error.
- Use functions to modularize code and improve readability.
- Add comments to explain the script's purpose and complex logic.