Using subshell to pass parameters with spaces

Question

I have a shell called "name_value.sh" that I want to pass parameters generated in a sub-shell. How can I ensure the command receiving parameters from the sub shell retain spaces?

NOTE: This is an extremely simplified example of what I am doing. Please read completely before responding.

A simplified example is:

./name_value.sh $(echo "no_spaces"; echo "with spaces")

Where name_value.sh looks like this:

#!/bin/bash
echo "Name=$1"
echo "Value=$2"

Desired output is:

Name=no_spaces
Value=with spaces

This is a greatly simplified example. My real sub shell is complex, loops and outputs dozens of name/value pair that must all be generated at the same time and passed to name_value.sh at the same time. I also have no control over the shell file I am calling.

I have tried echoing with quotes and using printf with "%q". I also considered putting the results of the subshell in an array first but can't get that to work either. I need the parent shell to interpret the sub shell as if the text were entered in place of the sub shell.

Answer 1

Yes. Set the IFS variable (which usually contains space,tab,newline) to be just a newline. That way, spaces and tabs will not be used for word splitting. This will give you your desired output.

IFS=$'\n'
set -o noglob # disable the second effect of leaving that
              # $(...) unquoted.
./name_value.sh $(echo "no_spaces"; echo "with spaces")

---

However, what I would do is have the script read from stdin.

# name_value.sh
IFS= read -r name
IFS= read -r value
echo "Name=$name"
echo "Value=$value"

then

( echo no_spaces; echo with spaces ) | ./name_value.sh

I think this approach is more robust.

Answer 2

When you use this command

./name_value.sh $(echo "no_spaces"; echo "with spaces")

The bash execute the "sub-shells" commands in "$()" and return the output string

Example

Input command: ./name_value.sh $(echo "no_spaces"; echo "with spaces")

Processed command: ./name_value.sh no_spaces with spaces

The next step is execute you bash script with three arguments

First argument: no_space

Second argument: with

Third argument: spaces

---

This is the same as calling the script manually with the command

./name_value.sh no_spaces with spaces

---

For solve you problem, you need to insert the quotes around the sub-shell call "$()"

You need this

./name_value.sh $(echo "no_spaces") "$(echo "with spaces")"

And you processed command is

./name_value.sh no_spaces "with spaces"

And finally, you output it will be

Name=no_spaces
Value=with spaces