XMLStarlet
Encyclopedia
XMLStarlet is a command line XML utility which allows the modification and validation of XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

 documents.

It is released under a MIT License
MIT License
The MIT License is a free software license originating at the Massachusetts Institute of Technology . It is a permissive license, meaning that it permits reuse within proprietary software provided all copies of the licensed software include a copy of the MIT License terms...

.

Example Usage

An XML document can be validated against an XSD schema as follows:

xml val -e -s my.xsd my.xml
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x
OK