erands
-n
operand non zero length
1
-z
operand has zero length
1
-d
there exists a directory whose ...
the opposite of -eq
2
=
the operands are equal (as strings)
2
!=
opposite of =
2
-lt
operand1 is ... string operators and numeric comparison operators as well. If the file argument to one of the primarie... is readable.
-s file
True if file exists and has a size greater than zero.
-t fd
True if file d
