6.6.7.12 -iquote, -I-

Any directories you specify with -I options before the -iquote options are searched only for the case of #include "file"; they are not searched for #include <file>.

If additional directories are specified with -I options after the -iquote, these directories are searched for all #include directives (ordinarily all -I directories are used this way).

In addition, the iquote option inhibits the use of the current directory (where the current input file came from) as the first search directory for #include "file." There is no way to override this effect of iquote. With -I. you can specify searching the directory that was current when the compiler was invoked. That is not exactly the same as what the preprocessor does by default, but it is often satisfactory.

iquote does not inhibit the use of the standard system directories for header files. Thus, iquote and -nostdinc are independent.