shared data sets on UNIX in C

[gwyn at BRL-VLD.ARPA]

From:      Doug Gwyn (VLD/VMB) <gwyn at BRL-VLD.ARPA>

Your shared data set problem can be solved by a facility known as
"record locking".  This is not in any standard UNIX kernel, but code
to implement it has been published (most recently in the reviewer's
guide for the /usr/group system interface standard).  In the absence of
such a facility, consider "file locking", which can be accomplished on
any UNIX system (if there is not a built-in facility for this, it can
be kludged up using links).  The last resort is to make a separate data
set manager process and route all data set access through this manager
(this works acceptably if you have FIFOs or perhaps sockets).