How to use the command 'indent' (with examples)

The ‘indent’ command is a utility that allows you to change the appearance of a C/C++ program by inserting or deleting whitespace. It is useful for automatically formatting code according to different styles and guidelines, making it easier to read and understand. The ‘indent’ command can be particularly beneficial when working on large codebases or collaborating with others.

Use case 1: Format C/C++ source according to the Linux style guide, automatically back up the original files, and replace with the indented versions

Code:

indent --linux-style path/to/source.c path/to/another_source.c

Motivation: In this use case, the ‘indent’ command is used to format C/C++ source files according to the Linux style guide. This ensures that the code is consistent with the Linux coding standards, making it easier for other developers to read and contribute to the project. By using the --linux-style option, the command automatically formats the code, saves backups of the original files, and replaces them with the newly indented versions. This is useful to maintain a clean and standardized codebase without losing the original files.

Explanation:

• --linux-style: The --linux-style option tells the ‘indent’ command to format the code according to the Linux style guide.
• path/to/source.c path/to/another_source.c: These are the paths to the C/C++ source files that need to be formatted.

Example output: The command will format the code in the specified source files according to the Linux style guide, creating backups of the original files and replacing them with the newly indented versions.

Use case 2: Format C/C++ source according to the GNU style, saving the indented version to a different file

Code:

indent --gnu-style path/to/source.c -o path/to/indented_source.c

Motivation: In this use case, the ‘indent’ command is used to format C/C++ source files according to the GNU style, which is commonly used in GNU projects. By using the --gnu-style option, the command automatically formats the code and saves the indented version to a different file. This is useful when you want to preserve the original file and have a separate file with the formatted code.

Explanation:

• --gnu-style: The --gnu-style option tells the ‘indent’ command to format the code according to the GNU style.
• path/to/source.c: This is the path to the C/C++ source file that needs to be formatted.
• -o path/to/indented_source.c: The -o option followed by the path specifies the output file where the indented version of the code will be saved.

Example output: The command will format the code in the specified source file according to the GNU style and save the indented version to the provided output file.

Use case 3: Format C/C++ source according to the style of Kernighan & Ritchie (K&R), no tabs, 3 spaces per indent, and wrap lines at 120 characters

Code:

indent --k-and-r-style --indent-level3 --no-tabs --line-length120 path/to/source.c -o path/to/indented_source.c

Motivation: In this use case, the ‘indent’ command is used to format C/C++ source files according to the style of Kernighan & Ritchie (K&R). This style is popular and widely used, particularly in legacy code or projects that adhere to the K&R conventions. By using the provided options, the command sets specific formatting rules such as no tabs, 3 spaces per indent, and wrapping lines at 120 characters. This ensures that the code follows the K&R style guide precisely.

Explanation:

• --k-and-r-style: The --k-and-r-style option tells the ‘indent’ command to format the code according to the Kernighan & Ritchie (K&R) style.
• --indent-level3: The --indent-level3 option sets the indentation level to 3, which means 3 spaces per indent.
• --no-tabs: The --no-tabs option ensures that tabs are not used for indentation.
• --line-length120: The --line-length120 option specifies that lines should be wrapped at 120 characters.
• path/to/source.c: This is the path to the C/C++ source file that needs to be formatted.
• -o path/to/indented_source.c: The -o option followed by the path specifies the output file where the indented version of the code will be saved.

Example output: The command will format the code in the specified source file according to the style of Kernighan & Ritchie (K&R), using 3 spaces per indent, no tabs, and wrapping lines at 120 characters. The indented version of the code will be saved to the provided output file.

Conclusion:

The ‘indent’ command is a powerful tool for formatting C/C++ source code according to different style guides and conventions. It allows you to automatically insert or delete whitespace to improve the appearance and readability of your code. By using the ‘indent’ command, you can ensure that your code follows a consistent style, making it easier to collaborate with others and maintain a clean and standardized codebase.