linux_programming/linux_programming_interface/solutions/chapter_5/exercise_5_1.c

/*
 * Modify the program in Listing 5-3 to use standard file I/O system calls (open() and
 * lseek()) and the off_t data type. Compile the program with the _FILE_OFFSET_BITS
 * macro set to 64, and test it to show that a large file can be successfully created.
 */

// for large file compile with: gcc -D_FILE_OFFSET_BITS=64 

#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

int
main (int argc, char *argv[])
{
  int fd;
  off_t off;
  if (argc != 3 || strcmp (argv[1], "--help") == 0)
    {
      printf ("%s pathname offset\n", argv[0]);
      return EXIT_FAILURE;
    }

  fd = open (argv[1], O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
  if (fd == -1)
    return EXIT_FAILURE;

  off = atoll (argv[2]);
  if (lseek (fd, off, SEEK_SET) == -1)
    return EXIT_FAILURE;

  if (write (fd, "test", 4) == -1)
    return EXIT_FAILURE;

  return EXIT_SUCCESS;
}