Have you looked at the split command?
$ split --helpUsage: split [OPTION] [INPUT [PREFIX]]Output fixed-size pieces of INPUT to PREFIXaa, PREFIXab, ...; defaultsize is 1000 lines, and default PREFIX is `x'. With no INPUT, or when INPUTis -, read standard input.Mandatory arguments to long options are mandatory for short options too. -a, --suffix-length=N use suffixes of length N (default 2) -b, --bytes=SIZE put SIZE bytes per output file -C, --line-bytes=SIZE put at most SIZE bytes of lines per output file -d, --numeric-suffixes use numeric suffixes instead of alphabetic -l, --lines=NUMBER put NUMBER lines per output file --verbose print a diagnostic to standard error just before each output file is opened --help display this help and exit --version output version information and exit

You could do something like:
split -l 200000 filename