What does this shell test achieve

Question

I have a very simple question that I can\'t answer. In shell, what would this command do:

test -d $VIRTUAL_ENV || virtualenv $VIRTUAL_ENV

It se

Answer 1

The || is the OR condition. Hence, this will test if $VIRTUAL_ENV directory exists. If not, it will run virtualenv $VIRTUAL_ENV.

Other examples:

$ test -d /tmp || echo "yes"
$
$ test -d /tmpblabla || echo "this dir does not exist"
this dir does not exist
$ test -d /tmp && echo "/tmp exists" || echo "yes"
/tmp exists