Conditional Statements

format                           "true" if:
---------------------------------------------------
(( _num1_ == _num2_ ))           numbers equal
(( _num1_ != _num2_ ))           numbers not equal
(( _num1_ < _num2_ ))            num1 < num2
(( _num1_ > _num2_ ))            num1 > num2
(( _num1_ <= _num2_ ))           num1 <= num2
(( _num1_ >= _num2_ ))           num1 >= num2

[[ _str1_ == _str2_ ]]           strings equal
[[ _str1_ != _str2_ ]]           strings not equal
[[ _str1_ < _str2_ ]]            str1 precedes str2
[[ _str1_ > _str2_ ]]            str1 follow str2
[[ _str1_ = _pattern_ ]]         str1 = pattern
[[ _str1_ != _pattern_ ]]        str1 != pattern
[[ -z _str_ ]]                   str is null
[[ -n _str_ ]]                   str is not null

[ x=y -o k=j ]                   or in expression
[ x=y -a k=j ]                   and in expression