Why is PWD empty and how to fix it?

I'm using lighttpd and wrote the following cgi script:

main(){
    printf("Content-ty开发者_如何学Gope: text/html\n\n");
    char * pwd ="";
    pwd=getenv("PWD");
    printf ("The current path is: %s",pwd);
}

The Result is

The current path is: (null)

Well, I don't get why. And I don't know how to find the path of the script executed. I'm looking for args[0] with a path, and used pwd for that, but maybe I should switch to something different.

UPDATE

Not working aswell is

char cwd[_PC_PATH_MAX+1];
getcwd(cwd, _PC_PATH_MAX+1);

cwd is " ". Maybe my script knew where it was if I stoped using room 1408 as my datacenter. :P

Use getcwd() instead. PWD isn't required to be set.

#include <unistd.h>

char *getcwd(char *buf, size_t size);

_PC_PATH_MAX is not the max path length. It's a key you pass to pathconf to request the max path length, as in pathconf("/", _PC_PATH_MAX). Of course if PATH_MAX is defined it would be simpler to use that directly.