How split a file in words in unix command line?

Using tr:

tr -s '[[:punct:][:space:]]' '\n' < file

Using sed:

$ sed -e 's/[[:punct:]]*//g;s/[[:space:]]\+/\n/g' < inputfile

basically this deletes all punctuation and replaces any spaces with newlines. This also assumes your flavor of sed understands \n. Some do not -- in which case you can just use a literal newline instead (i.e. by embedding it inside your quotes).

The simplest tool is fmt:

fmt -1 <your-file

fmt designed to break lines to fit the specified width and if you provide -1 it breaks immediately after the word. See man fmt for documentation. Inspired by http://everythingsysadmin.com/2012/09/unorthodoxunix.html