The following code gives
[: -ge: unary operator expected
when
i=0
if [ $i -ge 2 ]
then
#some code
fi
I need to add my 5 cents. I see everybody use [ or [[, but it worth to mention that they are not part of if syntax.
For arithmetic comparisons, use ((...)) instead.
((...)) is an arithmetic command, which returns an exit status of 0 if the expression is nonzero, or 1 if the expression is zero. Also used as a synonym for "let", if side effects (assignments) are needed.
See: ArithmeticExpression