How do builtins differ from external commands?

Builtins and external commands differ in several key ways:

1. Execution:

   • Builtins: Executed directly by the shell without spawning a new process. This makes them faster and more efficient for certain tasks.
   • External Commands: Require the shell to create a new process to run the command, which can introduce overhead.

2. Location:

   • Builtins: Part of the shell itself (e.g., bash, zsh). They are not stored as separate files on the filesystem.
   • External Commands: Stored as separate executable files in the filesystem (e.g., /bin/ls, /usr/bin/git).

3. Functionality:

   • Builtins: Often provide essential shell functionalities, such as changing directories (cd), setting environment variables (export), and controlling shell behavior (set).
   • External Commands: Typically perform specific tasks or operations, such as file manipulation, text processing, or network communication.

4. Environment Interaction:

   • Builtins: Can directly manipulate the shell's environment (e.g., changing the current directory affects the shell's state).
   • External Commands: Run in their own process and may not affect the shell's environment unless explicitly designed to do so (e.g., using output redirection or subshells).

Overall, builtins are integral to the shell's operation, while external commands provide additional functionality.