global: output usage on -h, --help, or no args before contacting mons

- when there are no arguments, print a short invitation to stderr to
  use -h or --help and exit with an error.
- if we get -h or --help, print usage to stdout, and exit with success.
- do the above *before* making any contact with the cluster.  we should
  not fail to explain usage because the mons are down.
- if there is some other error with the arguments, print an error message,
  but do not spam the user with usage.  Try to use cerr instead of derr.

Signed-off-by: Sage Weil <sage@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/librados-config.cc b/src/librados-config.cc
index a7fb69ba13c..1dbb7a101f6 100644
--- a/src/librados-config.cc
+++ b/src/librados-config.cc
@@ -37,6 +37,13 @@ int main(int argc, const char **argv)
 {
   vector<const char*> args;
   argv_to_vec(argc, argv, args);
+  if (args.empty()) {
+    cerr << argv[0] << ": -h or --help for usage" << std::endl;
+    exit(1);
+  }
+  if (ceph_argparse_need_usage(args)) {
+    usage_exit();
+  }
 
   bool opt_version = false;
   bool opt_vernum = false;