crushtool: warn usefully about missing output spec

When running with --test, you must request output to CSV files or
specific types of output to --show-X; make the error message
clarify what the tool wants.

Fixes: #3827
Signed-off-by: Dan Mick <dan.mick@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

diff --git a/src/crushtool.cc b/src/crushtool.cc
index 6584be54d5a8eb86809568e12a91c7d088790575..3cbd915a3215e32f44aca566aaa0ab00ad3ef33c 100644 (file)
--- a/src/crushtool.cc
+++ b/src/crushtool.cc
@@ -413,7 +413,7 @@ int main(int argc, const char **argv)
   }
 
   if (test && !display && !write_to_file) {
-    cerr << "WARNING: no output selected (via -o <filename>)" << std::endl;
+    cerr << "WARNING: no output selected; use --output-csv or --show-X" << std::endl;
     exit(EXIT_FAILURE);
   }