As you’ve already been told, it’s useful to read the manual – specifically this chapter – and even more specifically right here.
Specifically, you want
g++ -I/root/workingdirectory -I/root/workingdirectory2
Note also the documentation on #include directive syntax, described here as:
2.1 Include Syntax
Both user and system header files are included using the preprocessing
directive#include. It has two variants:#include <file>This variant is used for system header files. It searches for a file named file in a standard list of system directories. You can prepend directories to this list with the -I
option (see Invocation).#include "file"This variant is used for header files of your own program. It searches for a file named file first in the directory
containing the current file, then in the quote directories and then
the same directories used for<file>. You can prepend directories to
the list of quote directories with the -iquote option. The argument of
#include, whether delimited with quote marks or angle brackets,
behaves like a string constant in that comments are not recognized,
and macro names are not expanded. Thus,#include <x/*y>specifies
inclusion of a system header file named x/*y.However, if backslashes occur within file, they are considered
ordinary text characters, not escape characters. None of the character
escape sequences appropriate to string constants in C are processed.
Thus,#include "x\n\\y"specifies a filename containing three
backslashes. (Some systems interpret\as a pathname separator. All
of these also interpret/the same way. It is most portable to use
only/.)It is an error if there is anything (other than comments) on the line
after the file name.
So for example
#include "first.h"
will start looking in the same directory as the .cpp file containing this directive (or take a relative path as relative to this directory).
If you want to use the include path (specified by -I) you should use
#include <dir1/third.h>
Usual practice is to use the #include "local.h" form for headers inside a library/package/module (however you’ve chosen to organize that), and the #include <external.h> form for headers from external/3rd-party or system libraries.