fopen.c

/*
 * fopen.c
 */

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

/* This depends on O_RDONLY == 0, O_WRONLY == 1, O_RDWR == 2 */


FILE *fopen(const char *file, const char *mode)
{
  int flags = O_RDONLY;
  int plus = 0;
  int fd;

  while ( *mode ) {
    switch ( *mode ) {
    case 'r':
      flags = O_RDONLY;
      break;
    case 'w':
      flags = O_WRONLY|O_CREAT|O_TRUNC;
      break;
    case 'a':
      flags = O_WRONLY|O_CREAT|O_APPEND;
      break;
    case '+':
      plus = 1;
      break;
    }
    mode++;
  }

  if ( plus ) {
    flags = (flags & ~(O_RDONLY|O_WRONLY)) | O_RDWR;
  }

  fd = open(file, flags, 0666);

  if ( fd < 0 )
    return NULL;
  else
    return fdopen(fd, mode);
}