There is a standard command for file splitting - split.
For example, if I want to split a words file in several chunks of 10000 lines, I can use:
split -dl 10000 words wrd
and it would generate several files of the form wrd.01, wrd.02 and so on.
But I want to have a specific extension for those files - for example, I want to get wtd.01.txt, wrd.02.txt files.
Is there a way to do it?