1. The I/O streams user_input, user_output and user_error are closed if they are connected to a terminal (see tty property in stream_property/2). Input streams are rebound to a dummy stream that returns EOF. Output streams are reboud to forward their output to Stream.
2. The process is detached from the current process-group and its controlling terminal. This is achieved using setsid() if provided or using ioctl() TIOCNOTTY on /dev/tty.

To ignore all output, it may be rebound to a null stream. For example:

      ...,
      open_null_stream(Out),
      detach_IO(Out).

The detach_IO/1 should be called only once per process. Subsequent calls silently succeed without any side effects.

See also

detach_IO/0 and library(syslog).