Close a channel or a specific stream associated with it. For a job, {stream} can be one of "stdin", "stdout", "stderr" or "rpc" (closes stdin/stdout for a job started with "rpc":v:true) If {stream} is omitted, all streams are closed. If the channel is a pty, this will then close the pty master, sending SIGHUP to the job process. For a socket, there is only one stream, and {stream} should be omitted.