X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9DDB3395542A
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1614209239;
	bh=eGJWjkkp9g5pGgx5FIX66DsWgcFooMyX9eAsjCB035U=;
	h=Date:To:Subject:In-Reply-To:References:List-Id:List-Unsubscribe:
	 List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:
	 From;
	b=FqLVO9qjWgAFfOdEg1WVl+b/i7TRn6ut9+fj5DWyyjueVWvnz9IWI8pwsxG7ItSpu
	 W8wqbBsP3AjP9ryNKK6q/v9yw6J5WxtqL5LiT2e8c/KW9s15xeh357yl12CprXAqjU
	 W4j8QLNONbi+bX6xg2Lx+Uh4+M9ao34P4oRGWTNA=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org F00443857026
DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-05.nifty.com 11ONQlTE014828
X-Nifty-SrcIP: [118.243.85.178]
Date: Thu, 25 Feb 2021 08:26:54 +0900
To: cygwin AT cygwin DOT com
Subject: Re: Tee and file redirections are very slow to write anything.
Message-Id: <20210225082654.163452f107ae657ebbeb1c07@nifty.ne.jp>
In-Reply-To: <20210224224149.GM2979@dimstar.local.net>
References: <DB7PR02MB39960C1E938B80D9B98CF40DE79F9 AT DB7PR02MB3996 DOT eurprd02 DOT prod DOT outlook DOT com>
 <87eeh5b39n DOT fsf AT Otto DOT invalid>
 <49e01de1-f7de-5d60-2996-3c9afb834396 AT cs DOT umass DOT edu>
 <20210224224149 DOT GM2979 AT dimstar DOT local DOT net>
X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32)
Mime-Version: 1.0
X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00, DKIM_SIGNED,
 DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE,
 SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2
X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on
 server2.sourceware.org
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe: <https://cygwin.com/mailman/options/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive: <https://cygwin.com/pipermail/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe: <https://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: cygwin-bounces AT cygwin DOT com
Sender: "Cygwin" <cygwin-bounces AT cygwin DOT com>

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 DOT yano AT nifty DOT ne DOT jp>
--
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple