From 6e419a99f6b58817a8d39901a053ee752596cff8 Mon Sep 17 00:00:00 2001
From: Anthony Molinaro <anthony.molinaro@openx.com>
Date: Mon, 28 Mar 2016 10:55:45 -0700
Subject: provide eval command for nodetool and start script

---
 priv/templates/extended_bin | 11 ++++++++++-
 priv/templates/nodetool     | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/priv/templates/extended_bin b/priv/templates/extended_bin
index 3c71c84..d7a9a0b 100755
--- a/priv/templates/extended_bin
+++ b/priv/templates/extended_bin
@@ -449,9 +449,18 @@ case "$1" in
 
         relx_nodetool rpcterms $@
         ;;
+    eval)
+        # Make sure a node IS running
+        if ! relx_nodetool "ping" > /dev/null; then
+            echo "Node is not running!"
+            exit 1
+        fi
 
+        shift
+        relx_nodetool "eval" $@
+        ;;
     *)
-        echo "Usage: $REL_NAME {start|start_boot <file>|foreground|stop|restart|reboot|pid|ping|console|console_clean|console_boot <file>|attach|remote_console|upgrade|escript|rpc|rpcterms}"
+        echo "Usage: $REL_NAME {start|start_boot <file>|foreground|stop|restart|reboot|pid|ping|console|console_clean|console_boot <file>|attach|remote_console|upgrade|escript|rpc|rpcterms|eval}"
         exit 1
         ;;
 esac
diff --git a/priv/templates/nodetool b/priv/templates/nodetool
index b3cd247..1f409f5 100644
--- a/priv/templates/nodetool
+++ b/priv/templates/nodetool
@@ -52,9 +52,38 @@ main(Args) ->
                 Other ->
                     io:format("~p\n", [Other])
             end;
+        ["eval" | ListOfArgs] ->
+            % shells may process args into more than one, and end up stripping
+            % spaces, so this converts all of that to a single string to parse
+            String = binary_to_list(
+                      list_to_binary(
+                        string:join(ListOfArgs," ")
+                      )
+                    ),
+
+            % then just as a convenience to users, if they forgot a trailing
+            % '.' add it for them.
+            Normalized =
+              case lists:reverse(String) of
+                [$. | _] -> String;
+                R -> lists:reverse([$. | R])
+              end,
+
+            % then scan and parse the string
+            {ok, Scanned, _} = erl_scan:string(Normalized),
+            {ok, Parsed } = erl_parse:parse_exprs(Scanned),
+
+            % and evaluate it on the remote node
+            case rpc:call(TargetNode, erl_eval, exprs, [Parsed, [] ]) of
+                {value, Value, _} ->
+                    io:format ("~p\n",[Value]);
+                {badrpc, Reason} ->
+                    io:format("RPC to ~p failed: ~p\n", [TargetNode, Reason]),
+                    halt(1)
+            end;
         Other ->
             io:format("Other: ~p\n", [Other]),
-            io:format("Usage: nodetool {ping|stop|restart|reboot|rpc|rpcterms} [RPC]\n")
+            io:format("Usage: nodetool {ping|stop|restart|reboot|rpc|rpcterms|eval [Terms]} [RPC]\n")
     end,
     net_kernel:stop().
 
-- 
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