GNU bug report logs - #21908
find -f breaks pipes ?

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Flemming Gulager Danielsen <fgd <at> komplex-it.dk>
To: "bug-coreutils <at> gnu.org" <bug-coreutils <at> gnu.org>
Subject: find -f breaks pipes ?
Date: Fri, 13 Nov 2015 14:20:09 +0000

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Hi Guyz!

I am new here so if this is not the proper use of the maillist then I am sorry. I normally think I know my way around shells, but this I cant get the below to work. And I am wondering if it is a bug I need to report on tail util.

I run this command on a file.

tail -f testfile | tr -d H | grep e

while I in another shell

echo "Testing" >> testfile.

If leave out "| grep e" I get the output. I have tried with xargs echo {} also, but I get nothing if I go beond 2 pipes. It works fine if I go through a while read loop.

---
Med venlig hilsen / best regards
Flemming Danielsen
IT-Specialist
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Email:    fgd <at> komplex-it.dk<mailto:fgd <at> komplex-it.dk>
Mobil    +45 2026 9291
Telefon +45 8833 0478


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Message #8 received at 21908 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Flemming Gulager Danielsen <fgd <at> komplex-it.dk>, 21908 <at> debbugs.gnu.org
Subject: Re: bug#21908: find -f breaks pipes ?
Date: Fri, 13 Nov 2015 17:17:14 +0000

tag 21908 notabug
close 21908
stop

On 13/11/15 14:20, Flemming Gulager Danielsen wrote:
> Hi Guyz!
> 
> I am new here so if this is not the proper use of the maillist then I am sorry. I normally think I know my way around shells, but this I cant get the below to work. And I am wondering if it is a bug I need to report on tail util.
> 
> I run this command on a file.
> 
> tail -f testfile | tr -d H | grep e
> 
> while I in another shell
> 
> echo “Testing” >> testfile.
> 
> If leave out “| grep e” I get the output. I have tried with xargs echo {} also, but I get nothing if I go beond 2 pipes. It works fine if I go through a while read loop.

The data is buffered as detailed at:
http://www.pixelbeat.org/programming/stdio_buffering/

You can change the buffering with stdbuf. For e.g.:

  tail -f testfile | stdbuf -oL tr -d H | grep e

cheers,
Pádraig.

Message #11 received at 21908 <at> debbugs.gnu.org (full text, mbox):

From: Bernhard Voelker <mail <at> bernhard-voelker.de>
To: Pádraig Brady <P <at> draigBrady.com>,
 Flemming Gulager Danielsen <fgd <at> komplex-it.dk>, 21908 <at> debbugs.gnu.org
Subject: Re: bug#21908: find -f breaks pipes ?
Date: Sat, 14 Nov 2015 10:29:26 +0100

On 11/13/2015 06:17 PM, Pádraig Brady wrote:
> You can change the buffering with stdbuf. For e.g.:
> 
>   tail -f testfile | stdbuf -oL tr -d H | grep e

Additionally, depending on whether you furtherly process the output,
e.g. with yet another "| grep .", you see that grep also uses some
output buffering, so you may end up with:

 tail -f testfile \
   | stdbuf -oL tr -d H \
   | grep --line-buffered e \
   | grep .

Have a nice day,
Berny

Message #14 received at 21908 <at> debbugs.gnu.org (full text, mbox):

From: Bob Proulx <bob <at> proulx.com>
To: Flemming Gulager Danielsen <fgd <at> komplex-it.dk>
Cc: 21908 <at> debbugs.gnu.org
Subject: Re: bug#21908: find -f breaks pipes ?
Date: Sun, 15 Nov 2015 17:01:40 -0700

Flemming Gulager Danielsen wrote:
> I am new here so if this is not the proper use of the maillist then
> I am sorry.

Others answered your output buffering question.  Let me address the
mailing list question.

When you send a message to bug-coreutils it opens a bug ticket so that
we can track bugs and they won't get lost.  When asking a question
such as you are doing it is better to use the coreutils <at> gnu.org
mailing list instead.  That is a normal mailing list just for
discussion and no bug tickets opened.  It is the better place for
questions and discussion.

Bob

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