Node.js 的 createReadStreams/createWriteStreams 中 'flags' 选项的意义？

Question

fs.createReadStream/createWritStream 的 'flags' 选项有什么意义，而 fs 模块的 ReadStream 和 WriteStream 是不言自明的，无论它们是可读的还是可写？

Answer 1

Flag 选项允许您设置与写入或覆盖文件相关的不同行为。

例如，当创建一个 WriteStream 时，如果您传递标志 w 它将覆盖文件（如果存在）（这是默认值），而如果您使用标志 r+，如果文件存在，它只会修改文件，因为它实际打开文件进行读写，如果文件不存在，则会出错。

这是一个丢失的标志，那里是解释：

'r' - Open file for reading. An exception occurs if the file does not exist.
'r+' - Open file for reading and writing. An exception occurs if the file does not exist.
'w' - Open file for writing. The file is created (if it does not exist) or truncated (if it exists).
'w+' - Open file for reading and writing. The file is created (if it does not exist) or truncated (if it exists).
'a' - Open file for appending. The file is created if it does not exist.
'a+' - Open file for reading and appending. The file is created if it does not exist.