The XNATRestClient is deprecated. You should use XnatDataClient instead for on-going and future development.
XNATRestClient is a Java command-line tool that provides an easy way to script calls to the XNAT REST API. In many ways, XNATRestClient is similar to curl, although the syntax and usage is somewhat different. This tool is provided for platforms where curl may not be installed by default.e
XNATRestClient is provided as a bash shell script and a Windows batch file (where it's named XNATRestClient.bat) and is located in the bin folder of your xnat_builder. To configure XNATRestClient to work properly, all you should need to do is add that bin folder to your path variable or specify the path explicitly when you invoke the command.