subshells-use-parentheses-not-backticks

Subshells: use parentheses not backticks

To write a subshell command, you can use parentheses or backticks.

Example:

$(foo)  # yes
`foo`   # no

We prefer parentheses over backtick because parentheses are nestable.

Example:

$(foo $(goo $(hoo))

Be aware that escaping characters is slightly different, such as:

echo $(echo \$abc)
echo `echo \$abc`

Differences also exist for:

$(echo \`)
$(echo \\)

Thanks to http://stackoverflow.com/users/313821/peter-o