What does -f mean in bash

Question

I was looking at how to use runit to run gunicorn. I was looking at the bash file and I don\'t know what -f $PID does in

#!/bin/sh

GUNICORN=/us         


        

Answer 1

The [ is the same as the command test which allows you to test certain things. Try help test to find out what the flags are. Things to be careful with are spaces - the [ needs a space after it.