#include <fcntl.h> #include <stdio.h> #include <unistd.h> int main() { //Lose our fd and pull it again creat("fcntl.out", 0777); int newfd = open("fcntl.out", 0); int newfd2 = fcntl(newfd, F_DUPFD, 0); printf("fd %d duped into fd %d\n", newfd, newfd2); close(newfd); close(newfd2); }