文件打开的常量

以下常量旨在与 fs.open() 一起使用。

常量	描述
`O_RDONLY`	指示打开文件以进行只读访问的标志。
`O_WRONLY`	指示打开文件以进行只写访问的标志。
`O_RDWR`	指示打开文件以进行读写访问的标志。
`O_CREAT`	如果文件不存在则指示创建文件的标志。
`O_EXCL`	如果设置了 `O_CREAT` 标志并且文件已经存在，则指示打开文件应该失败的标志。
`O_NOCTTY`	标志表示如果路径标识一个终端设备，打开路径不应导致该终端成为进程的控制终端（如果进程还没有一个）。
`O_TRUNC`	标志表示如果文件存在并且是一个普通文件，并且该文件被成功打开以进行写访问，则其长度应被截断为零。
`O_APPEND`	指示数据将追加到文件末尾的标志。
`O_DIRECTORY`	如果路径不是目录，则表示打开应该失败的标志。
`O_NOATIME`	指示对文件系统的读取访问的标志将不再导致与文件关联的 `atime` 信息的更新。此标志仅在 Linux 操作系统上可用。
`O_NOFOLLOW`	如果路径是符号链接，则表示打开应该失败的标志。
`O_SYNC`	指示文件为同步 I/O 打开的标志，写操作等待文件完整性。
`O_DSYNC`	指示文件为同步 I/O 打开的标志，写操作等待数据完整性。
`O_SYMLINK`	指示打开符号链接本身而不是它指向的资源的标志。
`O_DIRECT`	设置后，将尝试最小化文件 I/O 的缓存影响。
`O_NONBLOCK`	指示在可能的情况下以非阻塞模式打开文件的标志。
`UV_FS_O_FILEMAP`	设置后，将使用内存文件映射来访问文件。此标志仅在 Windows 操作系统上可用。在其他操作系统上，此标志被忽略。

在 Windows 上，只有 O_APPEND、O_CREAT、O_EXCL、O_RDONLY、O_RDWR、O_TRUNC、O_WRONLY 和 UV_FS_O_FILEMAP 可用。

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.
`UV_FS_O_FILEMAP`	When set, a memory file mapping is used to access the file. This flag is available on Windows operating systems only. On other operating systems, this flag is ignored.

On Windows, only O_APPEND, O_CREAT, O_EXCL, O_RDONLY, O_RDWR, O_TRUNC, O_WRONLY, and UV_FS_O_FILEMAP are available.