Restore contents of a file descriptor after reading it?

Question

To give you a bit of context my program basically takes commands and pipes them together and records the amount of bytes of each output in a file.

My problem is that while I managed to pipe the processes together the moment I read the output of the first (to store the bytes in a file) the second process can't read the output because the file descriptor was already used.

Is their a way to restore the file descriptor before the read or to make a back up ?

Here's a sample code in the parent the goal of this code would be to store the output in the file and restore it to before reading it :

for (int i = 1; i < processes-1; i++) {
      
   close(apipe[i][1]); 
      FILE *fp;
      fp = fopen("count", "a");
      
      char buffer[4096];
      int amount=0;
      
      int std_fd=dup(apipe[i][0]);
      int count;
      while (1) {
            count = read(std_fd, buffer, sizeof(buffer));
            amount+=count;
            if (count == -1) {
            if (errno == EINTR) {
                continue;
            } else {
                perror("read");
                exit(1);
            }
            } else if (count == 0) {
                break;
            }
            else{
                break;}
     }
      fprintf(fp, "%d : %d \n", i,amount); 
      close(apipe[i][0]);
      if(i==1){
           close(apipe[0][0]); 
           close(apipe[0][1]);  
      }
      fclose(fp); 
      
}