Quoting command substitution

When we learn the inner works of a shell, we quickly realise the benefit of using double quotes with request for variable substitution.

For example, to assign a value to a variable (and preserve leading spaces), we would use:

$ address=" 23 Acacia Avenue "

A correct quotation is needed to recall the value complete with the spaces:

$ echo "<$address>"

The less known application of the quotes is when they are around the command substitution syntax. By default, POSIX shells remove trailing new-lines during command substitution. Double quotes change this behaviour!

Compare the output of the following commands:

$ echo $(ls)
log.1 log.2 log.3

and

$ echo "$(ls)"
log.1
log.2
log.3