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CompTIA Linux+ XK0-005 - 3.1 - Shell Script Elements - Built-in Commands: source

In shell scripting, the source command (also known as .) is a built-in command used to execute commands and load variables from a specified file into the current shell session. It is commonly used to include configuration files or reusable code snippets within scripts. The source command is particularly useful when you want to make variables and functions defined in another file available in your current script.

Using the source Command

The basic syntax for using the source command is as follows:

source filename

or

. filename
  • filename: The name of the file to be sourced. It can include a relative or absolute path.

When the source command is executed, it reads and executes the commands from the specified file in the current shell session. This means that any variables, functions, or other shell-specific configurations defined in the file will take effect in the current shell.

Benefits of Using the source Command

The source command provides several benefits in shell scripting:

  1. Code Reusability: You can create separate files containing reusable code snippets or configuration settings and easily incorporate them into multiple scripts using the source command. This helps in maintaining consistency and reduces code duplication.

  2. Variable Sharing: When you source a file, any variables defined in that file become accessible in the current script. This allows you to share variables across different scripts or load environment variables from configuration files.

  3. Function Availability: If a file contains function definitions, sourcing that file makes those functions available for use in the current script. This enables modular scripting and code organization.

Conclusion

The source command is a valuable tool in shell scripting for executing commands and loading variables from a specified file into the current shell session. It allows for code reusability, variable sharing, and function availability, making your scripts more flexible and modular. By leveraging the source command, you can enhance the functionality and maintainability of your shell scripts.

Remember to use the source command when you want to incorporate external code or configuration files into your scripts, ensuring that the variables and functions defined in those files are available in your current shell session.

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