-I /path/to/dir

Define the path to system header files for the c compiler. Normally the c compiler already knows where they are, but Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifif you want to use a different directory or Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifif your headers just are not in the standard location, you can use this option. It will pass two arguments to the c compiler:

/bin/sdcc --nostdinc -Command Line Options: -I /path/to/dir
Command line options for C compiler: -I /path/to/dirI/path/to/dir

The first one tells it to forget about the standard location for header files and the second one tells it where they actually are.

Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endifIf a partial path is used then your current working directory applies.

Note: include directories can also be added with the assembler directive Assembler directives: #cflags
Including C Source Files: #cflags#CFLAGS in your source file. There a partial path refers to the source file's directory!

Note: mind the space!