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From: Bill Paul <wpaul@FreeBSD.ORG>
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Date: Wed, 4 Feb 1998 08:30:04 -0800 (PST)
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To: tom@sdf.com, wpaul@FreeBSD.ORG, freebsd-bugs@FreeBSD.ORG
Subject: Re: bin/5571
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Synopsis: /var/yp/Makefile does not use temporary files properly

State-Changed-From-To: open-closed
State-Changed-By: wpaul
State-Changed-When: Wed Feb 4 08:22:26 PST 1998
State-Changed-Why: 
I have modified Makefile.yp in both -current and the 2.2.5 branch so
that it no longer needs to create /tmp/ypmake. The reason I had that there
in the first place is kind of dump. In a Makefile, if I say:

FOO = 'echo $$$$'

this does not, as you might expect, assign the current PID ($$) to FOO
and keep it there so that it can be referenced as $(FOO), thus yielding
the same PID each time. Instead, every time you reference $(FOO), it
gets re-evaluated, so multiple references to $(FOO) yields different PIDs
each time, which is not what I want. I tried to work around this by
writing the PID to a file once so that I could call up the same value
a couple different times without it changing unexpectedly.

What I did now was to simply append the two commands that need to use $$
together using a semicolon (yp_mkdb -o foo.$$; mv foo.$$ foo) so that
both commands are executed in the same subshell and thus the PID won't
change.

-Bill