How do builtins differ from executables?

Builtins and executables differ in several key ways:

1. Location:

   • Builtins: These commands are integrated into the shell itself. They do not exist as separate files on the filesystem.
   • Executables: These are standalone programs stored as files in the filesystem, typically located in directories like /bin or /usr/bin.

2. Execution:

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

3. Functionality:

   • Builtins: Often provide functionality that directly interacts with the shell environment, such as changing directories or setting shell variables.
   • Executables: Generally perform specific tasks or operations that may not directly affect the shell environment.

4. Availability:

   • Builtins: Available in every shell session as part of the shell's core functionality.
   • Executables: Availability depends on the system and the installed software; they may not be present on all systems.

In summary, builtins are commands that are part of the shell, while executables are separate programs that the shell can run.