GNU bug report logs - #13183
tail -f ignores SIGPIPE

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Message #18 received at control <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Ruediger Meier <sweet_f_a <at> gmx.de>
Cc: 13183 <at> debbugs.gnu.org
Subject: Re: bug#13183: tail -f ignores SIGPIPE
Date: Tue, 10 Feb 2015 15:14:59 +0000

unarchive 13183
tag 13183 - notabug
severity 13183 wishlist

On 14/12/12 14:33, Pádraig Brady wrote:
> tag 13183 + notabug
> close 13183
> stop
> 
> On 12/14/2012 02:04 PM, Ruediger Meier wrote:
>> Hi,
>>
>> I want to use tail and grep to follow a file until a particular pattern
>> appears. But tail does not exit when grep is finished.
>>
>> $ echo xxx > /tmp/blabla
>> $ tail -f /tmp/blabla |grep -m1 --line-buffered "xxx"
>> xxx
>>
>> Now tail still tries to read and exits only if I write again
>> into /tmp/blabla.
>>
>> Is this how it's supposed to be?
> 
> tail does exit on SIGPIPE, however it will
> only get the signal on write(), and so you
> need to get more data in the file before tail will exit.

It's a fair point though that tail, since it
can hang around forever should take special
steps to be responsive to the other end of the pipe going away.
I.E. it might use select() or poll(POLLHUP), to detect
immediately/periodically the other end of the pipe going away.

Pádraig.

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