Bash, confusing results for different file tests (test -f)

Question

I am confused in bash by this expression:

$ var=\"\" # empty var
$ test -f $var; echo $? # test if such file exists
0 # and this file exists, amazing!
$ test         


        

Answer 1

When var is empty, $var will behave differently when if quoted or not.

test -f $var          # <=> test -f       ==>   $? is 0
test -f "$var"        # <=> test -f ""    ==>   $? is 1

So this example tells us: we should quote the $var.