shell - Does variable=$(...) store the command or the result of the command in POSIX sh

Question

I was wondering: When I e.g. call

list=$(ps -ax)

is ps -ax executed once and I can read the value multiple times or is the command executed every time I call $list

Answer 1

Solution is, that the result is stored. To test that, I used the following script

    #!/bin/sh
    myTime=$(date)
    for a in 1 2 3 4
    do
        echo 'Stored command: '$myTime
        echo 'Fresh command: '$(date)
        sleep 2
    done 

Result looks like this:

Stored commandTue Sep 29 17:39:44 +02 2020
Fresh commandTue Sep 29 17:39:44 +02 2020
Stored commandTue Sep 29 17:39:44 +02 2020
Fresh commandTue Sep 29 17:39:46 +02 2020
Stored commandTue Sep 29 17:39:44 +02 2020
Fresh commandTue Sep 29 17:39:48 +02 2020
Stored commandTue Sep 29 17:39:44 +02 2020
Fresh commandTue Sep 29 17:39:50 +02 2020

Feel free to add missing tags; not sure about how to make stuff like $() most search engine friendly