The format is as follows

ffmpeg -i <input file> -ss <starting point> -t <length of capture> <output file>
ffmpeg -i Input_File.flv -ss 00:00:00 -t 00:10:00 Output_Filename.flv

http://www.surfthedream.com.au/blog/Archives/november-2008/how-to-split-a-movie-file-into-multiple-parts

Just finishing up brewing up some fresh ground comments...