This is an old revision of the document!

ffmpeg - Video - Duration

# Use perl-regex.
ffmpeg -i "input.mkv" -c copy -f null /dev/null 2>&1 | tail -n 1 | grep -Po "(?<=time=)([0-9]{1,2}:[0-9]{2}:[0-9]{2})"
 
or
 
# Use extended-regex.
ffmpeg -i "input.mkv" -c copy -f null /dev/null 2>&1 | tail -n 1 | grep -oE "[0-9]{1}:[0-9]{2}:[0-9]{2}"
 
or
 
ffmpeg -i "input.mkv" -c copy -f null /dev/null 2>&1 | grep -oE "[0-9]{1}:[0-9]{2}:[0-9]{2}" | tail -n 1
 
or
 
ffmpeg -i "input.mkv" 2>&1 | grep -oE "[0-9]{1}:[0-9]{2}:[0-9]{2}" | head -n 1

NOTE: This returns an estimate of the duration based on the bitrate and size of the file.