opendir.c

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

int main(){
  int fd;

  fd = open("/tmp", O_RDONLY);
  if ( fd < 0 ) {
    char err[] = "open failed";
    write(2, err, strlen(err));
    return 1;
  }

  while (1) {
    char buf[256];
    int read_size;

    read_size = read(fd, buf, sizeof(buf));

    if ( read_size > 0 ) {
      write(1, buf, read_size);
    } else if ( read_size == 0 ) {
      break;
    } else {
      char err[] = "read failed\n";
      write(2, err, strlen(err));
      write(2, strerror(errno), strlen(strerror(errno)));
      return 2;
    }
  }

  close(fd);
  return 0;
}