[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: weird bash pipe behavior

From: Yan Seiner
Subject: Re: weird bash pipe behavior
Date: Thu, 21 Jan 2010 06:11:10 -0800
User-agent: Mozilla-Thunderbird (X11/20090103)

Greg Wooledge wrote:
On Wed, Jan 20, 2010 at 07:34:35AM -0800, CptDpondo wrote:
mencoder .... 2>&1 | tr '\r' '\n' | grep -v -B 1 '^Pos'

this eventually creates the correct output, but it's buffered until
mencoder completes.  I have no idea why; the tr command streams
without buffering and I've used grep for years and never run into this

grep definitely has this buffering behavior.  If you're using GNU grep,
you can give it the --line-buffered option to change this, at least
according to whichever contributor added that one to

That is the correct solution. Apparently the behavior is not limited to grep; any process in a pipe that's longer than 2 can exhibit this. Something about libc behavior...

I replaced grep with awk, ran in to the same problem, and ended up using fflush() after scanning each line.

Interesting.  I learned something today.


  ,>/'_         o__
  (_)\(_)       ,>/'_          o__
A day may come  (_)\(_)         ,>/'_      o__
when the courage of men fails, (_)\(_) ,>/'_ when we forsake our friends and break all (_)\(_)
bonds of fellowship, but it is not this day.
It is not this day!
This day we ride!

reply via email to

[Prev in Thread] Current Thread [Next in Thread]