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Other useful variants are
$SPLUNK_HOME/bin/splunk btool validate-strptime $SPLUNK_HOME/bin/splunk btool validate-regex
Just run $SPLUNK_HOME/bin/splunk btool to see full syntax and options.
btool just outputs to standardout, so you see its output immediately on the commandline after entering that command.
For more convenient viewing, you can redirect the output to a file, or pipe it to a viewer like
more the usual way.