Utilizing ANSI Color Codes to Print Colored Text in Bash Terminal from a File

Learn how to effectively use ANSI color codes to print colored text to your bash terminal by manipulating file contents. This guide offers clear steps and best practices.
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How to Use ANSI Color Codes to Print Colored Text to Bash Terminal from a File

If you've ever wanted your terminal output to be easy on the eyes and informative, using colored text can be a game changer. In this post, we will address a common frustration where users want to print colored text from a file to the bash terminal but face difficulties getting it to work as expected.

The Problem

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Your goal is to print "Yes" in green and "No" in red as colored output on the terminal. While you have attempted to use a script utilizing ANSI escape codes, the output is not colored as intended. Instead, it looks something like this:

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Why the Original Approach Doesn’t Work

The reason for this issue centers around how variable expansion works in bash and the capabilities of tools like sed. When using single quotes in sed commands, variable references (like ${RED}) do not expand as expected, rendering your escape sequences as plain text instead of functioning codes.

The Solution Explained

Here’s a clear path to achieving the desired output using ANSI color codes in bash.

Step 1: Define Your Color Variables

First, you need to define your color variables properly. This is critical because you want the shell to understand these variables as escape sequences.

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Step 2: Modify Your Sed Command

You need to ensure that the sed command uses double quotes instead of single quotes so that variable expansion occurs. Here’s how you do that:

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Step 3: Print the Output

To print the content of your file with the proper formatting, you can simply use:

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Alternatively, if you want to leverage printf efficiently (which can interpret escape sequences), you can do:

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Additional Tips

Avoid Common Pitfalls:

Remember that using single quotes prevents variable expansion. Always use double quotes for commands that require it.

Overly complex piping with cat can lead to what’s called a "useless use of cat." Simplifying commands often leads to better performance and clarity.

Check for Errors:

Tools like shellcheck can help you catch errors in your scripts and suggest best practices.

Executing Scripts:

Conclusion

By following the steps outlined in this post, you can effectively employ ANSI color codes to enhance the visual representation of text in your bash terminal from a file. A bit of attention to how shell commands interact can go a long way in achieving your goals. Happy scripting!