Color output (ANSI escape codes) in Bash Scripting - Step-by-Step Execution

Concept Flow - Color output (ANSI escape codes)

Start Script

↓

Define Color Codes

↓

Print Text with Color

↓

Reset Color

↓

End Script

The script starts by defining color codes, then prints colored text, and finally resets the color to normal.

Execution Sample

Bash Scripting

RED='\033[31m'
RESET='\033[0m'
echo -e "${RED}Hello in Red${RESET}"

This script prints 'Hello in Red' in red color and then resets the color back to normal.

Execution Table

Step	Action	Variable/Code	Output	Notes
1	Define RED color code	RED='\033[31m'	No output	Sets RED to ANSI code for red text
2	Define RESET code	RESET='\033[0m'	No output	Sets RESET to ANSI code to reset color
3	Print colored text	echo -e "${RED}Hello in Red${RESET}"	Hello in Red (in red color)	Text appears red in terminal
4	End script	Script ends	No output	Colors reset to normal

💡 Script ends after printing colored text and resetting color

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
RED	undefined	\033[31m	\033[31m	\033[31m
RESET	undefined	undefined	\033[0m	\033[0m

Key Moments - 3 Insights

Why do we need to use the -e option with echo?

The -e option enables interpretation of backslash escapes like \033 for colors, as shown in step 3 of the execution_table.

What happens if we forget to reset the color after printing?

If RESET is not used, the terminal text color stays changed for all following outputs, as implied in step 4 where color reset happens.

Why are the color codes stored in variables instead of used directly?

Storing codes in variables makes the script cleaner and easier to reuse or change colors, as seen in steps 1 and 2.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what color will the text 'Hello in Red' appear?

A Green

B Red

C Blue

D Default terminal color

💡 Hint

Check the value of RED variable defined in step 1 and used in step 3.

At which step is the color reset to normal?

A Step 4

B Step 1

C Step 3

D Step 2

💡 Hint

Look at the notes column in the execution_table for when colors return to normal.

If we remove the -e option from echo in step 3, what happens?

A Text prints in red anyway

B Script fails with error

C Text prints with literal escape codes visible

D Text prints in default color without escape codes

💡 Hint

Refer to the key_moments about why -e is needed for escape code interpretation.

Concept Snapshot

Use ANSI escape codes to color terminal output.
Define color codes as variables like RED='\033[31m'.
Use echo -e to print colored text: echo -e "${RED}text${RESET}".
Always reset color after printing with RESET='\033[0m'.
Without reset, terminal color stays changed.

Full Transcript

This script shows how to print colored text in a terminal using ANSI escape codes. First, it defines RED as the escape code for red text and RESET as the code to reset colors. Then it prints 'Hello in Red' using echo with the -e option to interpret escape codes. Finally, it resets the color so the terminal returns to normal. The execution table traces these steps and the variable tracker shows how RED and RESET are set. Key moments explain why -e is needed and why resetting color is important. The quiz tests understanding of color usage and script behavior.