文件打开的常量

以下常量适用于 fs.open()。

常量	说明
`O_RDONLY`	表明打开文件用于只读访问。
`O_WRONLY`	表明打开文件用于只写访问。
`O_RDWR`	表明打开文件用于读写访问。
`O_CREAT`	表明如果文件尚不存在则创建该文件。
`O_EXCL`	表明如果设置了 `O_CREAT` 标志且文件已存在，则打开文件应该失败。
`O_NOCTTY`	表明如果路径是终端设备，则打开该路径不应该造成该终端变成进程的控制终端（如果进程还没有终端）。
`O_TRUNC`	表明如果文件存在且是常规文件、并且文件成功打开以进行写入访问，则其长度应截断为零。
`O_APPEND`	表明数据将追加到文件末尾。
`O_DIRECTORY`	表明如果路径不是目录，则打开应该失败。
`O_NOATIME`	表明文件系统的读取访问将不再导致与文件相关联的 `atime` 信息的更新。仅在 Linux 操作系统上可用。
`O_NOFOLLOW`	表明如果路径是符号链接，则打开应该失败。
`O_SYNC`	表明文件是为同步 I/O 打开的，写入操作将等待文件的完整性。
`O_DSYNC`	表明文件是为同步 I/O 打开的，写入操作将等待数据的完整性
`O_SYMLINK`	表明打开符号链接自身，而不是它指向的资源。
`O_DIRECT`	表明将尝试最小化文件 I/O 的缓存效果。
`O_NONBLOCK`	表明在可能的情况下以非阻塞模式打开文件。

The following constants are meant for use with fs.open().

Constant	Description
`O_RDONLY`	Flag indicating to open a file for read-only access.
`O_WRONLY`	Flag indicating to open a file for write-only access.
`O_RDWR`	Flag indicating to open a file for read-write access.
`O_CREAT`	Flag indicating to create the file if it does not already exist.
`O_EXCL`	Flag indicating that opening a file should fail if the `O_CREAT` flag is set and the file already exists.
`O_NOCTTY`	Flag indicating that if path identifies a terminal device, opening the path shall not cause that terminal to become the controlling terminal for the process (if the process does not already have one).
`O_TRUNC`	Flag indicating that if the file exists and is a regular file, and the file is opened successfully for write access, its length shall be truncated to zero.
`O_APPEND`	Flag indicating that data will be appended to the end of the file.
`O_DIRECTORY`	Flag indicating that the open should fail if the path is not a directory.
`O_NOATIME`	Flag indicating reading accesses to the file system will no longer result in an update to the `atime` information associated with the file. This flag is available on Linux operating systems only.
`O_NOFOLLOW`	Flag indicating that the open should fail if the path is a symbolic link.
`O_SYNC`	Flag indicating that the file is opened for synchronized I/O with write operations waiting for file integrity.
`O_DSYNC`	Flag indicating that the file is opened for synchronized I/O with write operations waiting for data integrity.
`O_SYMLINK`	Flag indicating to open the symbolic link itself rather than the resource it is pointing to.
`O_DIRECT`	When set, an attempt will be made to minimize caching effects of file I/O.
`O_NONBLOCK`	Flag indicating to open the file in nonblocking mode when possible.