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

size_t filesize(int fd)
{
  struct stat buffer;
  int status;
  status = fstat(fd, &buffer);
  return buffer.st_size;
}

size_t nlines(const char *file)
{
  size_t i, size;
  size_t num_lines = 0;
  int fd;
  char *map;  /* mmapped file */

  fd = open(file, O_RDONLY);
  if (fd == -1) {
    perror("Error opening file for reading");
    exit(EXIT_FAILURE);
  }

  size = filesize(fd);

  map = mmap(0, size, PROT_READ, MAP_SHARED, fd, 0);
  if (map == MAP_FAILED) {
    close(fd);
    perror("Error mmapping the file");
    exit(EXIT_FAILURE);
  }

  /* Read the file from the mmap */
  for (i = 0; i < size; ++i) {
    if(map[i] == '\n')
      num_lines++;
  }

  if (munmap(map, size) == -1) {
    perror("Error un-mmapping the file");
  }
  close(fd);
  return num_lines;
}

int main(int argc, char *argv[])
{
  if(argc > 1)
    printf("%s %d\n", argv[1], nlines(argv[1]));
  return 0;
}