These tools are used to convert XML and HTML to and from a line-oriented format more amenable to processing by classic Unix pipeline processing tools, like grep, sed, awk, cut, shell scripts, and so forth. There are four tools, xml2, 2xml, html2, and 2html. None of them take any command- line arguments; they are all simple filters, reading information from standard input in one format and writing the same information to standard output in a different format.