Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics

Dashboard
Notifications
Mark all as read
Q&A

How to prompt a user for an expanded variable in Bash?

+4
−0

I work with CentOS operating system and my only shell is Bash.

I want to create a script which prompts a user with a question like "What is your web application root?"
The user should answer directly in terminal and the answer would be stored in a variable named web_application_root.

I assume that generally the user would use variables such as ${HOME} (envar) or ${some_medium_directory} (non envar) in its answer, so any variable/s should be expanded.

How to prompt a user for an expanded variable?


I prefer not to use the read shell builtin for this because it requires IFS configuration which at least for now I find as an "overkill".
I don't think I would mind using Node.JS, Python, Perl or any "shell-completing" programming language if I have to, I just want to have something which is working and stable.

Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

3 comments

How would you want to take input from the user without using read in bash? What is so bad about IFS='' read ... that you would like to use another language instead? Is there more to your solution than simply setting one variable from the values of another? Why is web_application_root="${HOME}" (which makes the variable available and allows for env var expansion) not sufficient in your use case? Someone‭ 26 days ago

Also: When ${some_medium_directory} is not an env var, where does it come from? Someone‭ 26 days ago

Hello! Q1: I don't know :) Q2: I don't understand why IFS isn't on by default for read and to be honest I am not even sure I understand what it does. Q3: I am not sure I understand but probably there isn't more. Q4: web_application_root="${HOME}" is nice but I want to prompt the user for it as part of a bit larger interactive installation program which prompts for data by design. Q5: It might come from the user's preference to represent such a medium directory in a global variable. JohnDoea‭ 26 days ago

1 answer

+5
−0

How about this for bash:

#!/bin/bash

echo "What is your web application root?"
read web_application_root

web_application_root="$(envsubst <<< "$web_application_root")"

echo web_application_root=$web_application_root

envsubst does the environment variable expansion for you. For example:

$ ./test.sh 
What is your web application root?
${HOME}/a b
web_application_root=/home/Someone/a b
Why does this post require moderator attention?
You might want to add some details to your flag.

1 comment

Oh, finally something which works for me easily, thanks a lot ; I have tested echo $web_application_root before web_application_root="$(envsubst <<< "$web_application_root")" and after . Before I got a string and after I got a ROOT_DIRECTORY_NAME/the_rest, as expected. JohnDoea‭ 26 days ago

Sign up to answer this question »