XMLStarlet is a set of command line utilities (toolkit) to query, transform, validate, and edit XML documents and files using a simple set of shell commands in a way similar to how it is done with UNIX grep, sed, awk, diff, patch, join, etc commands.
This set of command line utilities can be used by those who want to test XPath query or execute commands on the fly as well as deal with many XML documents or for automated XML processing with shell scripts.