STREAMS-UX Programmer's Guide (February 2007)

Multiplexing
Persistent Links
Chapter 5
122
Characteristics of Persistent Links
Regular links created through I_LINK cannot be unlinked with I_PUNLINK. Similarly, persistent links created
through I_PLINK cannot be unlinked through I_UNLINK. The ioctl will return EINVAL when the
I_LINK/I_UNLINK and I_PLINK/I_PUNLINK calls are intermixed.
In a multilevel configuration where persistent links exist below a multiplexor whose stream is connected to
the above multiplexor by non-persistent links, closing the controlling stream will remove the non-persistent
links but persistent links will stay intact.
In a multilevel configuration where a non-persistent link exists below a multiplexor whose stream is
connected to the above multiplexor by persistent links, removing the persistent links will remove the
non-persistent links, if no other references to the lower streams exist.