On all operating systems, the default input/output/error streams can be redirected.

To specify redirection, set the stdin, stdout and stderr slots of a process to one of the following values:
f - default value; the stream is either inherited from the current process, or is a <process-stream> pipe
+closed+ - the stream is closed; reads will return end of file and writes will fail
+stdout+ - a special value for the stderr slot only, indicating that the standard output and standard error streams should be merged
a path name - the stream is sent to the given file, which must exist for input and is created automatically on output
an appender wrapping a path name - output is sent to the end of the given file, as with <file-appender>
a file stream or a socket - the stream is connected to the given Factor stream, which cannot be used again from within Factor and must be closed after the process has been started