Styling Terminal Output with ANSI Escape Codes

The Linux terminal, while powerful, often presents information in a basic, monochrome format. However, you can enhance readability and highlight specific parts of your output by adding color and styling. This is achieved using ANSI escape codes – special sequences of characters that the terminal interprets as formatting instructions.

What are ANSI Escape Codes?

ANSI escape codes are a standard for dictating text formatting within a terminal. They allow you to control things like text color, background color, text style (bold, underline, etc.), and cursor positioning. These codes are not displayed directly; the terminal interprets them and applies the corresponding formatting to the following text.

Basic Color Codes

Here’s a table of common ANSI escape codes for setting text color:

| Color | Code |
|———–|———|
| Black | \033[30m |
| Red | \033[31m |
| Green | \033[32m |
| Yellow | \033[33m |
| Blue | \033[34m |
| Magenta | \033[35m |
| Cyan | \033[36m |
| White | \033[37m |

You can also set background colors using codes 30 through 37 replaced with 40 through 47. For example, \033[41m sets the background color to red.

To reset the color to the default, use the code \033[0m. It’s crucial to include this reset code after your styled text to prevent the formatting from affecting subsequent output.

Applying Styles with echo and printf

You can utilize these escape codes with both echo and printf. However, echo requires the -e option to interpret backslash escapes, while printf handles them natively.

Example using echo:

RED='\033[0;31m'
NC='\033[0m' # No Color
echo -e "I ${RED}love${NC} Stack Overflow"

In this example:

• RED stores the ANSI escape code for red text.
• NC stores the ANSI escape code to reset the color.
• The -e option is essential for echo to interpret the escape sequences within the string. Without it, the escape codes will be printed literally.
• The ${RED} and ${NC} variables are expanded within the string, inserting the ANSI escape codes before and after the word "love".

Example using printf:

RED='\033[0;31m'
NC='\033[0m' # No Color
printf "I ${RED}love${NC} Stack Overflow\n"

printf doesn’t require the -e flag as it inherently interprets backslash escapes. The \n adds a newline character.

Beyond Color: Text Styles

ANSI escape codes also allow you to modify text styles:

• Bold: \033[1m
• Underline: \033[4m
• Reverse Video: \033[7m (Swaps foreground and background colors)

You can combine these styles and colors. For example, \033[1;31m sets the text to bold and red.

Best Practices

• Always reset the color: Include \033[0m after your styled text to prevent unwanted formatting.
• Use variables for codes: This improves readability and makes it easier to change styles later.
• Consider readability: Don’t overuse color and styles, as it can make output harder to read. Use them strategically to highlight important information.
• Test your codes: Verify that the ANSI escape codes work as expected in your terminal environment. Some terminals may have limited support for these codes.