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Date: Thu, 25 Feb 2021 08:26:54 +0900
To: cygwin@cygwin.com
Subject: Re: Tee and file redirections are very slow to write anything.
Message-Id: <20210225082654.163452f107ae657ebbeb1c07@nifty.ne.jp>
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From: Takashi Yano via Cygwin <cygwin@cygwin.com>
Reply-To: Takashi Yano <takashi.yano@nifty.ne.jp>
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On Thu, 25 Feb 2021 09:41:49 +1100
Duncan Roe wrote:
> On Wed, Feb 24, 2021 at 04:58:24PM -0500, Eliot Moss wrote:
> > On 2/24/2021 3:48 PM, ASSI wrote:
> > > Hamish McIntyre-Bhatty via Cygwin writes:
> > > > I found recently when trying to save output from a script for later
> > > > inspection that "tee" and file redirections seem to have massive
> > > > delays when run in Cygwin - usually nothing is written to file or
> > > > stdout until after the command has finished - not very helpful.
> > >
> > > You will want to switch from fully buffered to line-buffered or even
> > > unbuffered output.
> >
> > And this does not have to do with Cygwin.  The same happens on Linux.
> > The default is that terminal I/O is unbuffered while other stream are
> > buffered.  Pipes come under "other streams".  One can make programmatic
> > changes to get around this, but most programs won't override the
> > default behavior on their own ...
> >
> > Best -- Eliot Moss
> 
> The (Linux) default is that terminal I/O is *line* buffered
> 
> The man page for tee doesn't show an option to change buffering, while that for
> grep does.

However, in this case, output is not a 'terminal I/O' because it is
redirected to a file or a pipe.

Do these help?

"stdbuf -o L bash ./path/to/script.sh > stdout.log"
"stdbuf -o L bash ./path/to/script.sh | tee stdout.log"

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>
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