Path: utzoo!attcan!uunet!ns-mx!ceres!deimos.cis.ksu.edu!rutgers!ucsd!ucbvax!bloom-beacon!ITSTD.SRI.COM!wohler
From: wohler@ITSTD.SRI.COM (Bill Wohler)
Newsgroups: comp.windows.x
Subject: Re: redirecting stderr; passing arg lists
Message-ID: <8911281121.AA07183@milkfs.itstd.sri.com>
Date: 28 Nov 89 11:21:13 GMT
References: <8911081827.AA12003@turnpike.sun.com>
Sender: root@athena.mit.edu (Wizard A. Root)
Organization: SRI International, Heidelberg, W. Germany
Lines: 68

dan,

  thanks to you and ted nolan for helping me with my problem.  the
  reason i didn't reply sooner is that i had to do a bit of hacking to
  your solution.

  to snarf stderr, i piped and dupped as you said.  i also found that
  things worked better to make the pipes unbuffered since a newline
  was not always in the error messages.

  to check if there was any input to read in stderr, you suggested:

         ioctl(stderr_pipe[0], FIONREAD, &stuff_to_read);

     If (stuff_to_read == 0), then return.  NOTE: you should do that
     in the callback routine specified in XtAddInput anyway!  This is
     what Xt should be doing before it decides to call your callback
     routine (which is why it's "broken").

  this works great on my sun.  however, the x folks would not want to
  put this in their toolkit since the FIONREAD is documented not to
  support pipes in hpux and it is also documented not to be
  implemented at all on the 300 series (woe is me!)

  alternatively, i tried select, except that select still said that
  there was stuff in the input buffer after my read!  so that was of
  no use (unless someone can explain why this was so).

  my final solution was to use a non-blocking read.  appears to work
  great.  how inefficient or ugly is this?  here are the code
  fragments that work on both my sun (os 3.4) and hp (hp9000s300, os
  6.2). 

  dan, guess i still owe you a couple of bottles of weizen or so. ;-)

static
dbat_errinit()
{
	int stderr_pipe[2];		/* maybe needs to be static? */
	extern	int dbat_errdisp();

	(void)pipe(stderr_pipe);
	(void)dup2(stderr_pipe[1], fileno(stderr));
	(void)fcntl(stderr_pipe[0], F_SETFL, O_NDELAY);
	setbuf(stderr, NULL);
	XtAddTimeOut(ERRDISP_UPDATE*MSECPERSEC, dbat_errdisp, stderr_pipe[0]);
}

static
dbat_errdisp(client_data, id)
	caddr_t	client_data;
	XtIntervalId *id;
{
	int	fd = (int)client_data;
	register int chrs;
	char	buf[BUFSIZ];
	extern	int dbat_errdisp();

	buf[0] = '\0';
	chrs = read(fd, buf, sizeof(buf));

	if (buf[0]) {
		buf[chrs] = '\0';
		XwTextInsert(Errors, buf);
	}

	XtAddTimeOut(ERRDISP_UPDATE*MSECPERSEC, dbat_errdisp, fd);
}