Programming

include <sys/varargs.h>
int Open(const char *pathname,int oflag,...){
  int fd;
  va_list ap;
  mode_t mode;
  if(oflag & O_CREAT){
    va_start(ap,oflag);
    mode=va_arg(ap,va_mode_t);
    if((fd=open(pathname,oflag,mode))==-1)
       err_sys("open error for %s",pathname);
    va_end(ap);
  }
  else{
    if((fd=open(pathname,oflag))==-1)
       err_sys("open error for %s",pathname);
  }
  return(fd);
}