al_attach_shader_source_file - Allegro 5 API

       Like al_attach_shader_source(3alleg5) but reads the source code for the shader from the named file.

       Returns true on success and false on error, in which case the error log is updated.  The error log can be
       retrieved with al_get_shader_log(3alleg5).

       al_attach_shader_source_file - Allegro 5 API

al_attach_shader_source(3alleg5), al_build_shader(3alleg5), al_get_shader_log(3alleg5)

Allegro reference manual                                                   al_attach_shader_source_file(3alleg5)

       5.1.0

              #include <allegro5/allegro.h>

              bool al_attach_shader_source_file(ALLEGRO_SHADER *shader,
                 ALLEGRO_SHADER_TYPE type, const char *filename)