Скачать или смотреть How to Loop through an Array in Bash for Unlimited Values

Learn how to create a loop in Bash that cycles through array values endlessly, allowing for a dynamic and efficient programming approach.
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This video is based on the question https://stackoverflow.com/q/67956417/ asked by the user 'zeljko' ( https://stackoverflow.com/u/11296666/ ) and on the answer https://stackoverflow.com/a/67956765/ provided by the user 'Mikołaj Głodziak' ( https://stackoverflow.com/u/15407542/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Streamlining Array Value Loops in Bash

In the world of Bash scripting, efficiently handling loops can often pose a challenge, especially when you need to cycle through array values unlimited times. If you’ve ever found yourself stuck trying to loop through an array repeatedly, you’re in the right place. This guide will unravel a simple yet effective solution to this common problem.

The Problem

Imagine you have an array in Bash:

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You need to create a loop where a variable x takes on the values of the array (1, 2, 3, and then back to 1, 2, 3, and so on), while another variable i counts indefinitely (1, 2, 3… and so forth).

Your initial attempt might look something like this:

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However, the challenge lies in how to effectively loop through the elements of the array for the variable x.

The Solution

To achieve this, you can use the modulus operator to yield the correct index for accessing the array in a way that allows x to return to the start of the array once it reaches the end. Below is a code snippet that accomplishes this:

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Explanation of the Code

Initialize the Array: You start off by defining the array with values you want to loop through.

Count Elements: The expression ${# array[@ ]} counts the number of elements in the array, which helps in the modulus calculation.

Infinite Loop: The while true keeps the loop running indefinitely.

Modulus Calculation: The $i % $count_of_elements gives the remainder when i is divided by the number of elements in the array. This ensures that once i exceeds the array length, it resets to 0, allowing the loop to start over with the first element of the array.

Display Values: Using printf allows for neat output of the array values, separated by commas.

Increment: After each iteration, you increment i to move to the next index in the next cycle.

Flexibility

The great thing about this script is its flexibility. If you wish to change the input array, such as:

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The code remains valid and will continue to cycle seamlessly through the new array values.

Conclusion

With this simple Bash script, you can effectively loop through array values unlimited times while counting through an indefinite variable. Whether you are working on simple scripts or more complex applications, understanding how to manage array loops efficiently will significantly enhance your Bash scripting skills. Don’t hesitate to experiment with different values and configurations to see how versatile this approach can be!