Скачать или смотреть How to Run a Bash Script with User Input from a Text File

Discover how to run a Bash script multiple times using user input from a text file while handling prompts correctly.
---
This video is based on the question https://stackoverflow.com/q/64677999/ asked by the user 'JHH' ( https://stackoverflow.com/u/1226020/ ) and on the answer https://stackoverflow.com/a/64678092/ provided by the user 'hek2mgl' ( https://stackoverflow.com/u/171318/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Bash script running other bash scripts with user input

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Run a Bash Script with User Input from a Text File: A Step-by-Step Guide

If you've ever tried to run a Bash script that collects user input while looping through a list of items, you might have faced a frustrating issue. The problem arises when the read command is used in a loop; instead of prompting the user, it consumes lines from a file. This can result in your script failing to accept user input as expected. In this guide, we will explore this problem and provide a clear solution.

Understanding the Problem

Let’s walk through the example where you have:

A Bash script (hello.sh) that takes a name as an argument, prompts the user for their age, and then outputs a greeting.

A text file (names.txt) that contains a list of names, one per line.

A looping script (forall.sh) that reads through the names file and runs the hello.sh script for each name.

The Scenario

Here’s how the scripts are structured:

hello.sh

[[See Video to Reveal this Text or Code Snippet]]

names.txt

[[See Video to Reveal this Text or Code Snippet]]

forall.sh

[[See Video to Reveal this Text or Code Snippet]]

When you run forall.sh names.txt ./hello.sh, you might expect to be prompted for each user’s age. However, it doesn’t work as intended, and instead you receive output without the expected prompts for input.

Why It Happens

The crux of the issue lies in how input redirection works in Bash. When you run the foreach loop with input redirection using < $file, the standard input is set to read from the file. This means any read command inside hello.sh will not wait for user input but will instead consume lines from names.txt.

The Solution

To make sure your hello.sh script can still ask for user input while looping through names.txt, we need to explicitly specify which input source to use for user interaction. This can be accomplished by redirecting input from the terminal (/dev/tty) when calling the command.

Here’s how to modify your forall.sh script:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Solution

while read -r line; do: This loop reads each line from the text file.

if [ ! -z "$line" ]; then: This checks if the current line is not empty.

$command "$line" < /dev/tty: This runs the hello.sh script, passing the current name as an argument while ensuring that user input is taken from the terminal.

Expected Output

With this change, when you run forall.sh names.txt ./hello.sh, the output should now correctly prompt for each name’s age:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By redirecting user input specifically from the terminal using /dev/tty, you can effectively run your Bash script in a loop while still accepting interactive user input. This solution addresses the problem of standard input being consumed by the file redirect, allowing for a seamless user experience.

Now you can confidently loop through your text files and gather inputs without losing any interactivity with your scripts!