I am using ffmpeg to get the meta info of an audio clip. But I am unable to grep it.    $ ffmpeg -i 01-Daemon.mp3  |grep -i Duration    FFmpeg version SVN-r15261, Copyright (c) 2000-2008 Fabrice Bellard, et al.      configuration: --prefix=/usr --bindir=/usr/bin       --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib      --mandir=/usr/share/man --arch=i386 --extra-cflags=-O2       ...I checked, this ffmpeg output is directed to stderr.$ ffmpeg -i 01-Daemon.mp3 2> /dev/nullSo I think that grep is unable to read error stream to catch matching lines. How can we enable grep to read error stream?Using nixCraft link, I redirected standard error stream to standard output stream, then grep worked.$ ffmpeg -i 01-Daemon.mp3 2>&1 | grep -i Duration  Duration: 01:15:12.33, start: 0.000000, bitrate: 64 kb/sBut what if we do not want to redirect stderr to stdout?
How to grep standard error stream (stderr)?
grep;io redirection;ffmpeg