Linux indent Command with Practical Examples

Introduction

In this lab, you will learn how to use the Linux indent command to format C/C++ source code. The indent command is a powerful tool that can help you maintain consistent code formatting by indenting the code according to a specific set of rules. You will start by understanding the purpose and syntax of the indent command, then learn how to use it to format your C/C++ source code. Finally, you will explore how to customize the indent command options to suit your specific coding style preferences.

Linux Commands Cheat Sheet

Skills Graph

Understand the Purpose and Syntax of the indent Command

In this step, you will learn about the purpose and syntax of the indent command in Linux. The indent command is a tool used to format C/C++ source code by indenting it according to a specific set of rules.

To begin, let's explore the basic syntax of the indent command:

indent [options] input-file [output-file]

Here's a breakdown of the command:

• indent: This is the command name.
• [options]: These are the various options you can use to customize the formatting of the code.
• input-file: This is the file containing the C/C++ source code you want to format.
• [output-file]: This is the optional output file where the formatted code will be written. If not specified, the input file will be overwritten.

Some common options for the indent command include:

• -bad: Breaks function calls and declarations across lines.
• -bap: Breaks function parameters across lines.
• -bbo: Puts braces on "begin" lines.
• -nbc: Does not break function calls across lines.
• -br: Puts braces on "begin" lines.
• -brs: Puts braces on "begin" lines with a space.
• -ce: Puts comments to the right of code.
• -cli: Indents comments to the column specified.

Example output:

$ indent --help
Usage: indent [options] input-file [output-file]
Options:
  -bad       Break after boolean and arithmetic operators
  -bap       Break after parameters in function declarations
  -bbo       Put braces on "begin" lines
  -nbc       Don't break function calls across lines
  -br        Put braces on "begin" lines
  -brs       Put braces on "begin" lines with a space
  -ce        Put comments to the right of code
  -cli       Indent comments to column N
  ...

In the next step, you will learn how to use the indent command to format C/C++ source code.

Format C/C++ Source Code with the indent Command

In this step, you will learn how to use the indent command to format C/C++ source code.

First, let's create a sample C file to work with:

$ cd ~/project
$ nano sample.c

Add the following content to the sample.c file:

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

Now, let's use the indent command to format the source code:

$ indent sample.c

This will create a new file named sample.c.indent with the formatted code. You can also specify the output file directly:

$ indent sample.c -o formatted_sample.c

This will create a new file named formatted_sample.c with the formatted code.

Example output:

$ cat formatted_sample.c
#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

As you can see, the indent command has automatically indented the code and formatted it according to the default settings.

You can also customize the formatting by using various options. For example, to use the "Linux" style of formatting, you can run:

$ indent -linux sample.c -o formatted_sample.c

This will apply the "Linux" coding style to the formatted code.

In the next step, you will learn how to further customize the indent command options to fit your specific coding style.

Customize indent Command Options for Specific Coding Styles

In this step, you will learn how to customize the indent command options to format C/C++ source code according to specific coding styles.

The indent command provides a wide range of options to customize the formatting. Let's explore some common options and how they can be used:

1. Brace Placement:

   • -br (default): Put braces on "begin" lines.
   • -brs: Put braces on "begin" lines with a space.
   • -bl: Put braces on "begin" lines.

2. Indentation:

   • -i<number>: Set indentation level to <number> spaces.
   • -ci<number>: Set continuation indentation to <number> spaces.

3. Blank Lines:

   • -nbad: Do not break after boolean and arithmetic operators.
   • -nbap: Do not break function parameters.
   • -nbc: Do not break function calls.

4. Comment Formatting:

   • -c<number>: Set comment indentation to <number> columns.
   • -cd<number>: Set the maximum length of comments to <number> columns.

Let's try an example to format the sample.c file using the "GNU" coding style:

$ indent -gnu sample.c -o formatted_sample.c

This will format the source code using the "GNU" style, which follows the GNU coding standards.

Example output:

#include <stdio.h>

int
main ()
{
  printf ("Hello, World!\n");
  return 0;
}

As you can see, the indent command has applied the "GNU" coding style to the formatted code, including the brace placement and indentation.

You can explore the available options and experiment with different coding styles to find the one that best fits your project's requirements.

Summary

In this lab, you first learned about the purpose and syntax of the indent command in Linux. The indent command is a tool used to format C/C++ source code by indenting it according to a specific set of rules. You explored the basic syntax of the command and some common options for customizing the formatting. Then, you learned how to use the indent command to format C/C++ source code, including how to apply different formatting options and customize the output. Finally, you discovered how to use the indent command to enforce specific coding styles by leveraging its various configuration options.

Linux Commands Cheat Sheet