Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!uflorida!haven!adm!xadmx!moss@BRL.MIL
From: moss@BRL.MIL (VLD/VMB)
Newsgroups: comp.unix.questions
Subject: Re:  tail -f
Message-ID: <17785@adm.BRL.MIL>
Date: 13 Dec 88 03:34:56 GMT
Sender: news@adm.BRL.MIL
Lines: 17

>>I suppose it could use select(2)...
>
>You suppose incorrectly.  I know of no UNIX system where "select" will
>permit you to wait for a regular file (as in S_IFREG) file to be
>modified....
Right, he was probably referring to a non-blocking read which won't help
since blocking is really what you want.  Anyway, I haven't looked at the
source for 'tail', but I wrote an asynchronous log file monitoring
subroutine to allow the contents of an interactive program's log file to
be displayed in a scrolling window.  A subroutine gets called from an
alarm signal handler which loops on fgets() until one fails, then does a
clearerr() (only necessary on some systems like 4.2 BSD) to clear the EOF
condition.  Then, the signal handler resets the alarm for N seconds.  Of
course you can use sleep() instead of the alarm() call/handler if you
want.

-moss