xml: draft all but 3 most complex subcommands

pages/common/xml-pyx.md

@@ -1,8 +1,16 @@
 # xml-pyx
 
-> XMLStarlet toolkit: Convert XML documents to PYX format. (ESIS - ISO 8879).
+> Convert an XML document to PYX (ESIS - ISO 8879) format.
 > More information: <http://xmlstar.sourceforge.net/docs.php>.
 
+- Convert an XML document to PYX format:
+
+`xml pyx {{path/to/input.xml|URI}} >{{path/to/output.pyx}}`
+
+- Convert an XML document from standard input to PYX format:
+
+`cat {{path/to/input.xml}} | xml pyx >{{path/to/output.pyx}}`
+
 - Display help for `pyx` subcommand:
 
 `xml pyx --help`