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From: leh@atlantis.cis.ufl.edu (Les Hill)
Newsgroups: comp.unix.programmer
Subject: Re: using signal to (portably) wake up a select call
Keywords: select, signal, portability
Message-ID: <28427@uflorida.cis.ufl.EDU>
Date: 7 May 91 21:16:55 GMT
References: <2748@optima.cs.arizona.edu>
Sender: news@uflorida.cis.ufl.EDU
Reply-To: leh@atlantis.cis.ufl.edu (Les Hill)
Organization: U of Florida. Computer Science Dept.
Lines: 28

In article <2748@optima.cs.arizona.edu>, bakken@cs.arizona.edu (Dave Bakken) writes:
|> Is there a way to portably use signal (or something else) to
|> wake up a select call?
...stuff deleted...
|> In our application we just need to wake up the select call, but can't
|> afford to lose an IPC "poke," so if there is not sure way to avoid
|> this with signals (which seems to be the case, so far as I can ascertain)
|> then we will have to find something else.
...stuff deleted...
|> Dave Bakken                     Internet: bakken@cs.arizona.edu 

Are you sure you understnad the rudimentary aspects of select()?  You are not
going to lose an IPC poke by not having select() "running".
From the man page (SunOS 4.1.1):
     select() examines the I/O descriptor  sets  whose  addresses
     are  passed  in  readfds,  writefds, and exceptfds to see if
     some of their descriptors are ready for reading,  ready  for
     writing, or have an exceptional condition pending.
Unless you are reading and/or writing elsewhere, your FDs (if ready before
the call to select()) will cause the select() call to return immeadiately (the
so called "poke" :)

Perhaps what you want is asynchronous I/O (which is a different story.)
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