Basic Operation

Felix is designed to be used, in the first instance, like Python or other scripting language. You can just run a text file directly like this:

flx hello.flx

Behind the scenes, the flx command will first run the Felix compiler executable flxg generating some C++ files and some other information.

Then, it runs your chosen C++ compiler to compile and link those files to binary form.

Finally, it runs the binaries.

You do not need make, autoconf, or any kind of build script or configuration, it just works!

Where is the executable?

Felix puts the executable here:


where $HOME is your home directory. In other words, Felix uses a cache, which by default is


to store temporary files. Text files go in:


and binary files go in:


The file name used in the appropriate cache uses the prefix of the absolute pathname of the source file.

That’s a library not an executable!

You’re right! By default, Felix builds libraries, not programs, and it builds your program as a shared library. On Linux, this will have the extension .so, on OSX it will be .dylib and on Windows it will be .dll.

These library objects are loaded at run time by a small program executable, it will be called either flx_run or flx_arun, which can be found in build/release/host/bin. It will have extension .exe on Windows and no extension on unix like systems. This program is passed the absolute pathname of the library to load, which it does using dlopen() on unix like systems and LoadLibrary() on Windows.

How can I avoid rebuilding my program every time?

That’s easy. Make a cup of coffee. There’s nothing to do. Felix automatically checks dependencies and if it would compile the same program you have already compiled it just runs the already compiled one.

How can I make a standalone executable?

You can best do this like so:

flx --static -c -od . hello.flx

First, the –static switch says to do static linkage, instead of dynamic linkage. Second, the -c switch says to compile and link the program but not run it. Third, the -od . switch says to put the output of the build process into the current directory . using the basename of the source file hello as the basename of the executable.

On Unix systems hello will appear in the current directory and you can run it by


On Windows, hello.exe will appear instead, and you can run it by:


You can copy this program wherever you like and it will work, it does not need Felix anymore.

Note that for some complex programs which uses plugins, the program will have to be able to find the plugins, which are shared libraries or DLLs, and you will need to also set up an environment where it can do so. The flx program, even though a statically linked executable, can still load plugins.