subprocess.stdin
代表子进程的 stdin 的 Writable Stream。
如果子进程等待读取其所有输入,则在通过 end() 关闭此流之前,子进程将不会继续。
如果子进程衍生时 stdio[0] 设置为 'pipe' 以外的任何值,则此将是 null。
subprocess.stdin 是 subprocess.stdio[0] 的别名。
这两个属性将引用相同的值。
如果无法成功衍生子进程,则 subprocess.stdin 属性可能是 undefined。
A Writable Stream that represents the child process's stdin.
If a child process waits to read all of its input, the child will not continue
until this stream has been closed via end().
If the child was spawned with stdio[0] set to anything other than 'pipe',
then this will be null.
subprocess.stdin is an alias for subprocess.stdio[0]. Both properties will
refer to the same value.
The subprocess.stdin property can be undefined if the child process could
not be successfully spawned.