builtin - macOS

Overview

The builtin command in macOS is used to run a shell builtin, suppressing functionality of shell functions by the same name. Builtins are commands that are integrated directly into the shell itself rather than external executable programs. This command is particularly useful in scripting or interactive sessions to ensure that the original version of a command is used, rather than an overridden script or function.

Syntax

builtin [command] [arguments]

command: The name of the shell builtin command you want to execute.
arguments: Any arguments you want to pass to the builtin command.

The command’s behavior is strictly dependent on the builtin being invoked, and thus, it doesn’t have a universal set of options or flags.

Options/Flags

Since builtin is essentially a directive to use the shell’s in-built commands, it does not have specific options or flags itself. However, the options for the invoked command should be provided as if you were invoking the command directly.

Examples

Using echo as a builtin to avoid function overrides:
Suppose there is an overridden echo function in your environment. To use the shell’s original echo command, you would use:
```
builtin echo "This is the system's builtin echo, not the function!"
```
Forcing the builtin cd in a script:
Even if cd has been redefined, you can ensure you’re using the shell’s version:
```
builtin cd /path/to/directory
```

Common Issues

Conflicts with Aliases or Functions: A typical issue arises when aliases or functions shadow a builtin command. Using builtin explicitly avoids this by skipping function and alias lookup.
Lack of Error Handling: Since builtin directly invokes the builtin command, any error handling must be managed explicitly by the user, based on the error behavior of the builtin command itself.

Integration

You can combine builtin with other shell scripting features to ensure robust scripts that do not get affected by user-defined functions or aliases. For example:

#!/bin/bash

# Force use of builtin 'read' and 'echo'
builtin read -p "Enter your name: " name
builtin echo "Hello, $name, this uses the shell’s builtin echo!"

This ensures that the script behaves consistently across different environments.

alias – Define or display aliases.
unalias – Remove alias definitions.
type – Display information about command type (helpful to distinguish between builtins, functions, and external commands).

For a deeper understanding of builtins and their documentation, consult the shell’s manual page:

man bash

or online resources related to your specific shell if not using bash, as behaviors and available builtins might differ.