.. _man-handling-operating-system-variation:

*************************************
 Handling Operating System Variation
*************************************

When dealing with platform libraries, it is often necessary to provide special cases
for various platforms. The variable ``Sys.KERNEL`` can be used to write these special
cases. There are several functions intended to make this easier:
``is_unix``, ``is_linux``, ``is_apple``, ``is_bsd``, and ``is_windows``. These may be used as follows::

    if is_windows()
        some_complicated_thing(a)
    end

Note that ``is_linux`` and ``is_apple`` are mutually exclusive subsets of ``is_unix``\ .
Additionally, there is a macro ``@static`` which makes it possible to
use these functions to conditionally hide invalid code, as demonstrated in the following examples.

Simple blocks::

    ccall( (@static is_windows() ? :_fopen : :fopen), ...)

Complex blocks::

    @static if is_linux()
        some_complicated_thing(a)
    else
        some_different_thing(a)
    end

When chaining conditionals (including if/elseif/end),
the ``@static`` must be repeated for each level
(parentheses optional, but recommended for readability)::

    @static is_windows() ? :a : (@static is_apple() ? :b : :c)