The %if macro enables all the directives up to the %endif directive, if the condition is true. This is much like scripting languages. For example:

%if %{old_5x}

%define b5x 1

%undefine b6x

%endif

In this case, if the %old_5x macro has a value, the test will be true and all the directives inside the block will get executed.

A %else allows you to specify what to do if the test is not successful. For example:

%if %{old_5x}

%define b5x 1

%undefine b6x

%else

%define b6x 1

%undefine b5x

%endif

In this case, if the %old_5x macro has a value, then all the directives up to the %else will get executed. Otherwise, if the %old_5x macro has no value, the directives from the %else to the %endif will get executed.

Again, use an exclamation point to negate the test. For example:

%if ! %{old_5x}

%define b5x 1

%undefine b6x

%endif

You can use a && for an AND test. For example:

%if %{old_5x} && %{old_6x}

%{error: You cannot build for .5x and .6x at the same time}

%quit

%endif