split

split [options] [infile [prefix] ] Split infile into equal-sized segments. infile remains unchanged, and the results are written to prefixaa, prefixab, and so on. The default prefix is x, giving the output files xaa, xab, etc. If infile is - or missing, standard input is read. See also csplit.

Options
-a n, --suffix-length=n	Use suffixes of length n (default is 2).
-b n[b|k|m] , --bytes=n[b|k|m]	Split infile into n-byte segments. Alternate block sizes may be specified: b : 512 bytes. k : 1 kilobyte. m : 1 megabyte.
-C bytes[b|k|m] , --line-bytes=bytes[b|k|m]	Put a maximum of bytes into file; insist on adding complete lines.
-d, --numeric-suffixes	Use numeric suffixes instead of alphabetic suffixes for the output filenames.
-n, -l n, --lines=n	Split infile into n-line segments (default is 1000).
--help	Print a help message and then exit.
--verbose	Print a message for each output file.
--version	Print version information and then exit.

Examples
Break bigfile into 1000-line segments:

split bigfile

Concatenate four files, then split them into 10-line files named new.aa, new.ab, and so on. Note that without the -, new. would be treated as a nonexistent input file:
cat list[1-4] | split -10 - new.