How to use Linux host=${host:-"localhost"}

localhost=${host:-"localhost"}

The host variable is not set or empty, and the host takes the value after "-"; otherwise host= $host

host=${host-"localhost"}

The host variable is not set, and the host takes the value after "-", otherwise if the variable host is empty or has a value of host= $host

host=${host:-"localhost"}

Generally there is a read-p "Please enter a parameter:" Host

That is, when you are prompted for a parameter, but you enter directly, the host is empty, and localhost is the string as its value. Otherwise you will use the string you entered as the value

How to use Linux host=${host:-"localhost"}