Re: weird bash pipe behavior

[Greg Wooledge]

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
> behavior.

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
http://mywiki.wooledge.org/BashFAQ/009