What are the differences between built-in commands and external commands in Linux?

Built-in Commands vs. External Commands in Linux

In the Linux operating system, there are two main types of commands: built-in commands and external commands. Understanding the differences between these two types of commands is essential for effectively navigating and utilizing the Linux command-line interface.

Built-in Commands

Built-in commands, also known as shell commands, are commands that are integrated directly into the shell (the command-line interpreter) itself. These commands are typically executed by the shell without the need to load a separate program or executable file.

Some key characteristics of built-in commands:

1. Faster Execution: Built-in commands are generally faster to execute than external commands because they are part of the shell and do not require the shell to load a separate program.

2. Limited Functionality: Built-in commands have a more limited set of functionalities compared to external commands, as they are designed to perform specific, commonly used tasks within the shell.

3. Shell-specific: Built-in commands are specific to the shell you are using, such as Bash, Zsh, or Fish. The available built-in commands may vary depending on the shell.

4. Examples: Some common built-in commands in Bash include cd (change directory), echo (print text to the console), export (set environment variables), and exit (exit the shell).

External Commands

External commands, on the other hand, are standalone programs or executable files that are stored in the file system, typically in directories like /bin, /usr/bin, or /usr/local/bin. These commands are executed by the shell by searching for and running the corresponding executable file.

Characteristics of external commands:

1. Broader Functionality: External commands generally have a wider range of functionalities compared to built-in commands, as they are standalone programs that can perform more complex tasks.

2. Slower Execution: External commands take longer to execute than built-in commands because the shell needs to locate and load the executable file before running it.

3. Cross-shell Compatibility: External commands are typically compatible across different shells, as they are not tied to a specific shell implementation.

4. Examples: Some common external commands in Linux include ls (list directory contents), mkdir (create a directory), grep (search for patterns in text), and git (version control system).

Here's a Mermaid diagram to visualize the differences between built-in and external commands:

In summary, built-in commands are integrated into the shell and are generally faster to execute, but have a more limited set of functionalities. External commands, on the other hand, are standalone programs with broader capabilities, but take longer to execute and are more cross-shell compatible. Understanding the differences between these two types of commands can help you effectively navigate and utilize the Linux command-line interface.