OK, here goes.

I have to write a program, in which I need to use strtok and dup2 to redirect one file to another, but I need to also have the user to actually put the command cat < file1 > file2, but not from the shell, but instead by using my program. That's why I need strtok. And the reason my program doesn't work is probably because of that, because I don't really understand how strtok works. I found a similar program on the internet, but they just take the ls command and redirect it to the file. That's it. My program is much more complicated. I mean, it would've been easier just to say in shell cat < file1 > file2, but for some reason they want us to do it this way. So, anyways, here is what I have so far (here I just combined what I have found on the internet with what I already had from before. We had to do something similar but then the user would just go ls or ls -l. Very simple stuff. This is much harder, for me, at least.)

 #include <fcntl.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
 #include <sys/wait.h>
 #include <string.h>


 int main() {
     pid_t pid;
     char line[256];
     char *args[129];
     int i;
     int fd;
     int status;
     char *temp;

     while (1) {
            printf(">");
            if (fgets(line, 256, stdin) == 0) {
                 exit(0);
        }
            else {
            pid = fork();
            if (pid == 0) {
                i = 0;
                temp = strtok("<",line);
                while (temp != NULL) {
                   args[i++] = temp;
                   temp = strtok(">",line);
                   args[i] = '\0';
                 }
                fd = open("hello", O_RDONLY);
                dup2(fd, STDIN_FILENO);
                fd = open("world", O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU);
                dup2(fd, STDOUT_FILENO );
                close(fd);
                execvp(args[0], args); 
               } 

              else {
                  close(fd);
                  wait(&status);
              }
            }
       } 
    }

Any help would be greatly appreciated.