1. const (
    2.     O_RDONLY int = syscall.O_RDONLY // 只读模式打开文件
    3.     O_WRONLY int = syscall.O_WRONLY // 只写模式打开文件
    4.     O_RDWR   int = syscall.O_RDWR   // 读写模式打开文件
    5.     O_APPEND int = syscall.O_APPEND // 写操作时将数据附加到文件尾部
    6.     O_CREATE int = syscall.O_CREAT  // 如果不存在将创建一个新文件
    7.     O_EXCL   int = syscall.O_EXCL   // 和O_CREATE配合使用，文件必须不存在
    8.     O_SYNC   int = syscall.O_SYNC   // 打开文件用于同步I/O
    9.     O_TRUNC  int = syscall.O_TRUNC  // 如果可能，打开时清空文件
    10. )
    1. const (
    2.     // Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
    3.     O_RDONLY int = syscall.O_RDONLY // open the file read-only.
    4.     O_WRONLY int = syscall.O_WRONLY // open the file write-only.
    5.     O_RDWR   int = syscall.O_RDWR   // open the file read-write.
    6.     // The remaining values may be or'ed in to control behavior.
    7.     O_APPEND int = syscall.O_APPEND // append data to the file when writing.
    8.     O_CREATE int = syscall.O_CREAT  // create a new file if none exists.
    9.     O_EXCL   int = syscall.O_EXCL   // used with O_CREATE, file must not exist.
    10.     O_SYNC   int = syscall.O_SYNC   // open for synchronous I/O.
    11.     O_TRUNC  int = syscall.O_TRUNC  // truncate regular writable file when opened.
    12. )