Include files

If a line in a makefile starts with the string include or sinclude followed by white space (at least one <SPACE> or <TAB> character), the rest of the line is assumed to be a file name. (This name can contain macros.) The contents of the file are placed at the current location in the makefile.

For include, a fatal error occurs if the file is not readable. For sinclude, a non-readable file is silently ignored.