Question

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

int main (int argc, char* argv[]) 

{

  char* filename = argv[1]; 

  /* Open the file for writing. If it exists, append to it; 

     otherwise, create a new file.  */ 

  int fd = open (filename, O_RDONLY | O_CREAT | O_APPEND, 0666); 

// Reading file probleme

  close (fd); 

  return 0; 

} 

My problem is that I can’t really find how to read to buffer. I have only ints in the file but how can I read from it to that buffer? I can’t find functions to achieve that.

Answer 1

The function you’re looking for is called “read”. You have to pass it a buffer you’ve already allocated previously, however. Something like this ought to work:

if (fd) {
  char buffer[1024];
  int n = read(fd, buffer, 1024);

  /* ... */
}

after that call, n will contain the number of bytes read from the fd (or 0 for none or less than 0 if an error occured).

If you have raw ints in that file, you could then access them kinda like this:

int *ibuffer = (int*)buffer;

ibuffer is then an array of ints of length 1024/sizeof(int) containing the first n/sizeof(int) consecutive ints in fd. Strictly speaking this isn’t quite legal C, but then I haven’t seen an architecture lately where this wouldn’t have worked.