Problem with fgets and double printing

Hello! I'm trying to read from a text file that's being redirected to my program.

Code:

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./program < test.txt

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The code looks like this:

Code:

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  // read redirection
  char buffer[50][200] = {0};

  int size = 0;
  while(fgets(buffer[size], 200, stdin) != NULL) {
    printf("%s", buffer[size]);
    size++;
  }
 
  printf("\nPrinting Array\n");
  for(int i=0; i < size; i++) {
    printf("%s", buffer[i]);
  }


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Is this the best way to do it? I feel like I have a lot of extra space/size because I'm not sure how long the commands or text file will be. Should I be reading the length of the text file somehow?

Additionally, I thought of setting the last element to NULL, but apparently I can't do something along the lines of

Code:

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buffer[size+1] = NULL;

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Why exactly does C stop me from doing this? And how would I mark the end of the buffer array?