Can you use a function call as a condition in an if statement?

Question

here's what i'm trying to achive:

function f1() {
  return 0
}

function f2() {
  return 0
}

if [[ f1 && f2 ]]; then
  echo "success"
else
  echo "fail"
fi

Answer 1

You don't use [[ (or [) when running a command and checking the result code.

if f1 && f2 ; then
  echo "success"
else
  echo "fail"
fi