By default subprocess inherits stdin of parent process. To change this this option can be set to a resource ID (rid) of an open file, "inherit", "piped", or "null":

• number: the resource ID of an open file/resource. This allows you to read from a file.
• "inherit": The default if unspecified. The subprocess inherits from the parent.
• "piped": A new pipe should be arranged to connect the parent and child sub-process.
• "null": This stream will be ignored. This is the equivalent of attaching the stream to /dev/null.