The third argument to main()

myenv.c

/*  It turns out that the environment pointer is passed to main()
    as the third argument -- I had no idea!  The usual way to get
    the environment is via an "extern char **environ;" declaration. 

    This program prints out the environment in KEY=VALUE format,
    one variable per line.
*/

#include <stdio.h>

int main(int argc, char **argv, char **envp) {
  while (*envp) 
    printf("%s\n", *envp++);
  return 0;
}

Awesome.