5 Dec
2024
5 Dec
'24
11:22 p.m.
Regarding pipes and pipe-like interprocess communications facilities in
other operating systems, VMS has always had a pipe-like communications
pseudo-devices called mailboxes. The main difference between Unix pipes
and VMS mailboxes is that pipes have distinct read-only and write-only file
descriptors. Mailboxes do not--channels (VMS-speak for file descriptors)
assigned to a mailbox can be used for both reading and writing. This means
that it is not possible to do "broken pipe"-type detection on a mailbox.
This very much restricts the usefulness of mailboxes.
I wrote a true pipe device driver for VMS as part of the DEC Shell product
(a port of the Unix Bourne shell to VMS).
-Paul W.