int main(int argc, char *argv[]){
int fd[2];
if(pipe(fd)==-1) exit(1);
if(fork() > 0)
parent(fd, argv);
else child(fd, argv);
}
void parent(int *fd, char *argv[]){ // A writer
close(fd[0]);
dup2(fd[1], 1); // 1 is the standard output
close(fd[1]); // close original file descriptor
execlp(argv[1], argv[1], "a.out", NULL);
}
void child(int *fd, char *argv[]){ // A reader
close(fd[1]);
dup2(fd[0], 0); // 0 is the standard input
close(fd[0]); // close original file descriptor
execlp(argv[2], argv[2], "-c", NULL);
}