Bash - Catch input for a substituted command stored in variable

Question

How would I be able to catch the input for a substituted command stored in a variable?

Example:

How would I be able to catch the input for the following command?

bar_foo=$(openssl passwd -1 -salt "foobar")

Answer 1

The approach you're showing above would catch the output from the subcommand, ie. $(...) into your variable, $bar_foo. When using openssl you can provide the password using either the -in or the -stdin switches.

Example

$ myvar=$(openssl passwd -1 -salt "foobar" -stdin <<< "blah")
$ echo $myvar
$1$foobar$1ips4/cyJvjUjCj8w4exx0

It's generally advisable to put the password in a file and then call openssl, since that'll keep it out of your history and shield it from being exposed too openly.

UPDATE #1

The OP ended up using this method to prompt the user for their password using read and then storing it in a variable, pass1.

$ read -p "Password: " -s pass1

This variable could then be used as input to the openssl command.

$ myvar=$(openssl passwd -1 -salt "foobar" -stdin <<< "$pass1")
$ echo $myvar
$1$foobar$1ips4/cyJvjUjCj8w4exx0