The standard include directories usually can be controlled by the user through compiler options. The standard C++ library and the standard C library are implicitly included in these standard include directories. Typical implementations search only standard include directories. The intent of this syntax is to search for the files under control of the implementation. Note that the Arduino IDE only uses -I, so there is little to no distinction between and '.'.Ĭommonly the main usage of the distinction is to use to include system or library headers, and '.' to include headers that are part of the actual sketch / application, since the 'current directory' is automatically added as a local include path. If dir begins with =, then the = will be replaced by the sysroot prefix see -sysroot and -isysroot.

Search dir only for header files requested with #include 'file' they are not searched for #include, before all directories specified by -I and before the standard system directories. If the directory dir is a standard system include directory, the option is ignored to ensure that the default search order for system directories and the special treatment of system headers are not defeated. Directories named by -I are searched before the standard system include directories. searches the 'system' paths, while '.' searches both the system an 'local' paths.Īdd the directory dir to the list of directories to be searched for header files. The proper distinction is exactly what paths are searched for the include files.

Arduino wire h library