bash which OR operator to use - pipe v double pipe

Question

When I'm looking at bash script code, I sometimes see | and sometimes see ||, but I don't know which is preferable.

I'm trying to do something like ..

set -e;

ret=0 && { which ansible || ret=$?; }

if [[ ${ret} -ne 0 ]]; then
    # install ansible here
fi

Please advise which OR operator is preferred in this scenario.

Answer 1

| isn't an OR operator at all. You could use ||, though:

which ansible || {
  true # put your code to install ansible here
}

This is equivalent to an if:

if ! which ansible; then
  true # put your code to install ansible here
fi

---

By the way -- consider making a habit of using type (a shell builtin) rather than which (an external command). type is both faster and has a better understanding of shell behavior: If you have an ansible command that's provided by, say, a shell function invoking the real command, which won't know that it's there, but type will correctly detect it as available.