#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>

// Not an ideal implementation of cat -n by far, but it is a start
// 
// CSE 271 
// January 2007

// This file contains two improvements over what we had in class:
//    - It does not print a line number unless it knows there is content
//      for the line.
//    - It uses a 4 character-wide line number (%4d) so that the columns
//      line up (at least for the first 9999 lines of a file).

int main(int argc, char *argv[])
{
  int filetoread;
  char c;
  int done = 0;
  int result;
  int line=0;
  char last;

  if (argc < 2) {
    printf("We need an argument.\n");
    return -1;
  }
  
  /* open a file */
  filetoread = open(argv[1], O_RDONLY);
  if (filetoread == -1) {
    printf("File is not found.\n");
    return -1;
  }

  last = '\n';  // so that we print a line first
  
  while (done == 0) {
    /* read the file */
    result = read(filetoread, &c, 1);
    if (result < 1)
      done=1;
    else {
      if(last == '\n') {
        line++;
        printf("%4d ", line);  
      }

      /* print content to the screen */
      result = putchar(c);
      if (result == EOF) {
	printf("Output failure.\n");
	return -1;
      }
      last = c;
    }
  }

  /* close the file */
  close(filetoread);
  
  return 0;
}