Split text file into smaller multiple text file using command line

I know the question has been asked a long time ago, but I am surprised that nobody has given the most straightforward unix answer:

split -l 5000 -d --additional-suffix=.txt $FileName file

• -l 5000: split file into files of 5,000 lines each.
• -d: numerical suffix. This will make the suffix go from 00 to 99 by default instead of aa to zz.
• --additional-suffix: lets you specify the suffix, here the extension
• $FileName: name of the file to be split.
• file: prefix to add to the resulting files.

As always, check out man split for more details.

For Mac, the default version of split is apparently dumbed down. You can install the GNU version using the following command. (see this question for more GNU utils)

brew install coreutils

and then you can run the above command by replacing split with gsplit. Check out man gsplit for details.