Very Computer

I'm writing a fairly large script that is essenially a frontend to other
programs/scripts & I want to redirect stderr to a file and see it on the
screen as well, thus allowing any error messages to be captured to file,
while also letting any prompts/messages passed through stderr to appear on
the screen.

My issue is this:
I'm using the following code which works, but I'm getting a delay of about
~2seconds between when the message is written to stderr and when it appears
on the screen (obviously because of where/how I'm sending it):

[$ErrLog is also written to by other means, such as through 'print', so
$ErrLog.screen is needed - otherwise everything I write to $ErrLog will show
on the screen, when we only want stderr]

...<declarations,etc. (incl. $ErrLog)>...
exec 2>>$ErrLog.screen
tail -f $ErrLog.screen|tee -a $ErrLog &
...<script continues>...

It is this delay I would like to get rid of, but I can't seem to reduce it.
I have tried renice-ing it with different values in the following way, but
with no apparent effect:

...<declarations,etc. (incl. $ErrLog)>...
exec 2>>$ErrLog.screen
(tail -f $ErrLog.screen|tee -a $ErrLog) &
renice -n <newvalue> $!
...<script continues>...

Can anyone help me?

OS/Shell:
UnixWare 7.1.1 i386 x86at SCO UNIX_SVR5
KSH Version M-12/28/93e-SCO

TIA
Jason

Quote:>I'm writing a fairly large script that is essenially a frontend to other
>programs/scripts & I want to redirect stderr to a file and see it on the
>screen as well, thus allowing any error messages to be captured to file,
>while also letting any prompts/messages passed through stderr to appear on
>the screen.

  >(list)

e.g.,

| $ echo foo > foo
| $ cat foo.sh
| #!/bin/bash
| exec 1> >(tee -a foo)
| exec 2>&1
| echo "test1" >&1
| echo "test2" >&2
| echo "test3" >&2
| echo "test4" >&1
| $ ./foo.sh
| test1
| test2
| test3
| test4
| $ cat foo
| foo
| test1
| test2
| test3
| test4

if that doesn't work perhaps script(1) is your friend, e.g.,

| $ echo foo > foo
| $ cat foo.sh
| #!/bin/bash
| echo "test1" >&1
| echo "test2" >&2
| echo "test3" >&2
| echo "test4" >&1
| $ SHELL=$PWD/foo.sh script -a foo
| Script started, file is foo
| test1
| test2
| test3
| test4
| Script done, file is foo
| $ cat -t foo
| foo
| Script started on Fri Sep 14 15:31:34 2001
| test1^M
| test2^M
| test3^M
| test4^M
|
| Script done on Fri Sep 14 15:31:34 2001

--
okay, have a sig then

Quote:> I'm writing a fairly large script that is essenially a frontend to other
> programs/scripts & I want to redirect stderr to a file and see it on the
> screen as well, thus allowing any error messages to be captured to file,
> while also letting any prompts/messages passed through stderr to appear on
> the screen.

> My issue is this:
> I'm using the following code which works, but I'm getting a delay of about
> ~2seconds between when the message is written to stderr and when it
appears
> on the screen (obviously because of where/how I'm sending it):

> [$ErrLog is also written to by other means, such as through 'print', so
> $ErrLog.screen is needed - otherwise everything I write to $ErrLog will
show
> on the screen, when we only want stderr]

> ...<declarations,etc. (incl. $ErrLog)>...
> exec 2>>$ErrLog.screen
> tail -f $ErrLog.screen|tee -a $ErrLog &
> ...<script continues>...

I've done similar things before.  The best thing I came up with was
to use tee, but I put this in a 2nd wrapper, so that your big script
has it's own tiny wrapper, like this,

--begin tiny wrapper--
  your-big-script 2>&1 | tee -a $errlog
--end tiny wrapper--

So you actually run the tiny wrapper script, and it executes your big
script using the tee to save a copy of the output.  However, this method
probably won't work for stderr only.  I recommend you look at using
some kind of coprocess, such as available in ksh.

--
David Thompson

Foster City, CA  USA