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How To Create a Shell Script Rotation Animation

Ubuntu 7

Creating a shell script rotation animation can be a fun and educational exercise. It combines various shell scripting concepts such as loops, sleep commands, and character manipulation. In this article, we’ll explore different methods of creating a rotation animation using shell script.

Quick Answer

To create a shell script rotation animation, you can use various methods such as using a while loop and a for loop, using a while loop and printf, using the fish shell, or using printf in a minimal way. These methods involve manipulating characters and using sleep commands to create the rotation effect.

Understanding Shell Script Animation

Shell script animation is a way to create visual effects directly in your terminal. It’s often used to create loading indicators or other visual feedback. One common type of animation is a rotation animation, where a character or a set of characters appear to rotate in place.

Method 1: Using a while loop and a for loop

The first approach involves using a while loop and a for loop. Here’s the code:

#!/bin/bash

chars="/-\|"

while :; do
 for (( i=0; i<${#chars}; i++ )); do
 sleep 0.5
 echo -en "${chars:$i:1}" "\r"
 done
done

In this script, we define a variable chars which holds the characters we want to rotate. The while :; do command creates an infinite loop. Inside this loop, we have a for loop that iterates over each character in chars.

The sleep 0.5 command pauses execution for 0.5 seconds. The echo -en "${chars:$i:1}" "\r" command prints the current character and a carriage return (\r), which moves the cursor back to the start of the line, effectively overwriting the previous character.

Method 2: Using a while loop and printf

The second approach involves using a while loop and the printf command. Here’s the code:

#!/usr/bin/env bash

spinner() {
 local i sp n
 sp='/-\|'
 n=${#sp}
 printf ' '
 while sleep 0.1; do
 printf "%s\b" "${sp:i++%n:1}"
 done
}

printf 'Doing important work '
spinner &

sleep 10 # sleeping for 10 seconds is important work

kill "$!" # kill the spinner
printf '\n'

In this script, we define a function spinner that creates the rotation animation. The sp variable holds the characters to rotate, and n is the length of sp.

Inside the spinner function, we have a while loop that prints each character from sp and then moves the cursor back one column using the \b escape sequence. This overwrites the previous character. The spinner function runs in the background, and the main script sleeps for 10 seconds before killing the spinner and printing a newline.

Method 3: Using the fish shell

If you’re using the fish shell, you can create a rotation animation like this:

set -l symbols â—· â—¶ â—µ â—´
while sleep 0.5
 echo -e -n "\b$symbols[1]"
 set -l symbols $symbols[2..-1] $symbols[1]
end

In this script, we use an array variable symbols to hold the characters to rotate. The while loop rotates the contents of symbols and prints the first element. The \b escape sequence moves the cursor back one column to overwrite the previous character.

Method 4: Using printf in a minimal way

Here’s another approach that uses printf in a minimal way:

while true ; do
 for i in \\ "|" / "-"; do
 printf "$i"
 sleep 0.1
 printf "\b"
 done
done

This script uses a while loop and a for loop to iterate through the characters \\, |, /, and -. It uses printf to print each character and then moves the cursor back one column using \b to overwrite the previous character. There is a 0.1-second delay between each change.

Conclusion

Creating a rotation animation using shell script can be a fun way to learn more about shell scripting. Whether you’re using bash, fish, or another shell, you can use these techniques to create your own animations. Remember to experiment with different characters and delays to create the effect you want. Happy scripting!

What is a shell script rotation animation?

A shell script rotation animation is a visual effect created using shell scripting techniques to make characters appear to rotate in place within a terminal.

What are some common use cases for shell script animation?

Shell script animation is often used to create loading indicators, progress bars, or other visual feedback in terminal-based applications.

What programming languages can be used to create shell script rotation animations?

Shell script rotation animations can be created using shell scripting languages such as bash or fish. These languages provide the necessary tools and commands to manipulate characters and create visual effects in the terminal.

How does the first method using a `while` loop and a `for` loop work?

In the first method, a while loop creates an infinite loop, and a for loop iterates over each character in a defined set of characters. The sleep command introduces a delay between each character, and the echo command with the -en flag prints the current character and moves the cursor back to the start of the line to overwrite the previous character.

How does the second method using a `while` loop and `printf` work?

The second method uses a while loop and the printf command to create the rotation animation. The printf command prints each character from a defined set of characters and uses the \b escape sequence to move the cursor back one column, effectively overwriting the previous character. The animation runs in the background, allowing other commands to be executed simultaneously.

Can shell script rotation animations be created in the fish shell?

Yes, shell script rotation animations can be created in the fish shell. The fish shell supports similar techniques using arrays and the echo command with the -e flag to interpret escape sequences. The \b escape sequence is used to move the cursor back one column and overwrite the previous character.

What is the purpose of the `sleep` command in shell script rotation animations?

The sleep command is used to introduce a delay between each character change in the rotation animation. This delay controls the speed of the rotation and allows the animation to be visually understandable to the user.

Are there any other methods to create shell script rotation animations?

Yes, there are multiple methods to create shell script rotation animations. The examples provided in this article demonstrate different approaches using while loops, for loops, and the printf command. You can also experiment with different characters, delays, and techniques to create your own unique rotation animations.

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