I noticed the following comment and some code in the
popen() source code:
/* The current PIPE: device only supports unidirectional connections. */
Starting with OS4 pipes are bidirectional so this should
probably be enhanced for OS4 users.
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This is hard to do, since you cannot ask a file system or handler to volunteer version information, or provide you with a list of its properties. Hence, the popen() code makes assumptions which, provided you don't have a Kickstart 2.x/3.x queue-handler installed, will hold.