diff --git a/src/conf_parse.erl b/src/conf_parse.erl
index 98301ee..0a4bf68 100644
--- a/src/conf_parse.erl
+++ b/src/conf_parse.erl
@@ -92,6 +92,14 @@ file_test() ->
         ], Conf),
     ok.
 
+shell_value_test() ->
+    Conf = conf_parse:file("test/shell_value.conf"),
+    ?assertEqual([
+            {["value1"], {shell, "cat value1"}},
+            {["value2"], "43"}
+        ], Conf),
+    ok.
+
 utf8_test() ->
     Conf = conf_parse:parse("setting = thing" ++ [338] ++ "\n"),
     ?assertEqual([{["setting"],
@@ -152,7 +160,7 @@ parse(Input) when is_binary(Input) ->
 
 -spec 'setting'(input(), index()) -> parse_result().
 'setting'(Input, Index) ->
-  p(Input, Index, 'setting', fun(I,D) -> (p_seq([p_zero_or_more(fun 'ws'/2), fun 'key'/2, p_zero_or_more(fun 'ws'/2), p_string(<<"=">>), p_zero_or_more(fun 'ws'/2), fun 'value'/2, p_zero_or_more(fun 'ws'/2), p_optional(fun 'comment'/2)]))(I,D) end, fun(Node, _Idx) ->
+  p(Input, Index, 'setting', fun(I,D) -> (p_seq([p_zero_or_more(fun 'ws'/2), fun 'key'/2, p_zero_or_more(fun 'ws'/2), p_string(<<"=">>), p_zero_or_more(fun 'ws'/2), p_choose([fun 'value'/2, fun 'shell_value'/2]), p_zero_or_more(fun 'ws'/2), p_optional(fun 'comment'/2)]))(I,D) end, fun(Node, _Idx) ->
     [ _, Key, _, _Eq, _, Value, _, _ ] = Node,
     {Key, Value}
  end).
@@ -166,7 +174,7 @@ parse(Input) when is_binary(Input) ->
 
 -spec 'value'(input(), index()) -> parse_result().
 'value'(Input, Index) ->
-  p(Input, Index, 'value', fun(I,D) -> (p_one_or_more(p_seq([p_not(p_choose([p_seq([p_zero_or_more(fun 'ws'/2), fun 'crlf'/2]), fun 'comment'/2])), p_anything()])))(I,D) end, fun(Node, Idx) ->
+  p(Input, Index, 'value', fun(I,D) -> (p_one_or_more(p_seq([p_not(p_choose([p_seq([p_zero_or_more(fun 'ws'/2), fun 'crlf'/2]), fun 'comment'/2, fun 'shell_value'/2])), p_anything()])))(I,D) end, fun(Node, Idx) ->
     case unicode:characters_to_binary(Node, utf8, latin1) of
         {_Status, _Begining, _Rest} ->
             {error, {conf_to_latin1, line(Idx)}};
@@ -175,6 +183,21 @@ parse(Input) when is_binary(Input) ->
     end
  end).
 
+-spec 'shell_value'(input(), index()) -> parse_result().
+'shell_value'(Input, Index) ->
+  p(Input, Index, 'shell_value', fun(I,D) -> (p_seq([p_zero_or_more(fun 'ws'/2), fun 'shell_start'/2, p_zero_or_more(fun 'ws'/2), p_zero_or_more(p_seq([p_not(fun 'shell_end'/2), p_anything()])), fun 'shell_end'/2]))(I,D) end, fun(Node, _Idx) ->
+    [_, _, _, Cmd, _] = Node,
+    {shell, unicode:characters_to_list(Cmd)}
+ end).
+
+-spec 'shell_start'(input(), index()) -> parse_result().
+'shell_start'(Input, Index) ->
+  p(Input, Index, 'shell_start', fun(I,D) -> (p_string(<<"`">>))(I,D) end, fun(_Node, _Idx) ->ws end).
+
+-spec 'shell_end'(input(), index()) -> parse_result().
+'shell_end'(Input, Index) ->
+  p(Input, Index, 'shell_end', fun(I,D) -> (p_string(<<"`">>))(I,D) end, fun(Node, Idx) ->transform('shell_end', Node, Idx) end).
+
 -spec 'comment'(input(), index()) -> parse_result().
 'comment'(Input, Index) ->
   p(Input, Index, 'comment', fun(I,D) -> (p_seq([p_zero_or_more(fun 'ws'/2), p_string(<<"#">>), p_zero_or_more(p_seq([p_not(fun 'crlf'/2), p_anything()]))]))(I,D) end, fun(_Node, _Idx) ->comment end).
@@ -198,7 +221,7 @@ parse(Input) when is_binary(Input) ->
   p(Input, Index, 'ws', fun(I,D) -> (p_one_or_more(p_charclass(<<"[\s\t]">>)))(I,D) end, fun(_Node, _Idx) ->ws end).
 
 
-
+transform(_,Node,_Index) -> Node.
 -file("peg_includes.hrl", 1).
 -type index() :: {{line, pos_integer()}, {column, pos_integer()}}.
 -type input() :: binary().
diff --git a/src/conf_parse.peg b/src/conf_parse.peg
index 4813e14..29e25e5 100644
--- a/src/conf_parse.peg
+++ b/src/conf_parse.peg
@@ -55,7 +55,7 @@ line <- ((setting / comment / ws+) (crlf / eof)) / crlf %{
 
 %% A setting is a key and a value, joined by =, with surrounding
 %% whitespace ignored.
-setting <- ws* key ws* "=" ws* value ws* comment? %{
+setting <- ws* key ws* "=" ws* (value / shell_value) ws* comment? %{
     [ _, Key, _, _Eq, _, Value, _, _ ] = Node,
     {Key, Value}
 %};
@@ -66,8 +66,8 @@ key <- head:word tail:("." word)* %{
     [unicode:characters_to_list(H)| [ unicode:characters_to_list(W) || [_, W] <- T]]
 %};
 
-%% A value is any character, with trailing whitespace stripped.
-value <- (!((ws* crlf) / comment) .)+ %{
+%% A value is any character except a shell value or comment, with trailing whitespace stripped.
+value <- (!((ws* crlf) / comment / shell_value) .)+ %{
     case unicode:characters_to_binary(Node, utf8, latin1) of
         {_Status, _Begining, _Rest} ->
             {error, {conf_to_latin1, line(Idx)}};
@@ -76,6 +76,16 @@ value <- (!((ws* crlf) / comment) .)+ %{
     end
 %};
 
+%% A shell value is a shell command wrapped around '$(' ')'
+shell_value <- ws* shell_start ws* (!shell_end .)* shell_end %{
+    [_, _, _, Cmd, _] = Node,
+    {shell, unicode:characters_to_list(Cmd)}
+%};
+
+%%% These are the delimiters for shell values
+shell_start <- "`" `ws`;
+shell_end <- "`";
+
 %% A comment is any line that begins with a # sign, leading whitespace
 %% allowed.
 comment <- ws* "#" (!crlf .)* `comment`;
@@ -175,6 +185,14 @@ file_test() ->
         ], Conf),
     ok.
 
+shell_value_test() ->
+    Conf = conf_parse:file("test/shell_value.conf"),
+    ?assertEqual([
+            {["value1"], {shell, "cat value1"}},
+            {["value2"], "43"}
+        ], Conf),
+    ok.
+
 utf8_test() ->
     Conf = conf_parse:parse("setting = thing" ++ [338] ++ "\n"),
     ?assertEqual([{["setting"],
diff --git a/src/cuttlefish_conf.erl b/src/cuttlefish_conf.erl
index 250d4d5..c9b8321 100644
--- a/src/cuttlefish_conf.erl
+++ b/src/cuttlefish_conf.erl
@@ -74,13 +74,34 @@ file(Filename) ->
             {_, Values} = lists:unzip(Conf),
             case cuttlefish_error:filter(Values) of
                 {errorlist, []} ->
-                    remove_duplicates(Conf);
+                    % expand any non-literal values (ie. shell values)
+                    expand_values(Filename, remove_duplicates(Conf));
                 {errorlist, ErrorList} ->
                     NewErrorList = [ {error, {in_file, {Filename, E}}} || {error, E} <- ErrorList ],
                     {errorlist, NewErrorList}
             end
     end.
 
+expand_values(Filename, Conf) ->
+    lists:map(fun({K, {shell, Cmd}}) ->
+                      % run the shell command, capture the result
+                      % and that will be the new value, all shell
+                      % processing will be relative to the directory
+                      % where the conf filename being processed is located
+                      % first get the current cwd so we can restore it later
+                      {ok, Cwd0} = file:get_cwd(),
+                      file:set_cwd(filename:dirname(Filename)),
+                      ShellValue = os:cmd(Cmd),
+                      % restore the original cwd
+                      file:set_cwd(Cwd0),
+                      % strip all linefeed/carriage return from the end
+                      {K, re:replace(ShellValue, "[\n\r]", "", [global, {return, list}])};
+                 (Value) ->
+                      % normal value, nothing to do
+                      Value
+              end,
+              Conf).
+
 -spec generate([cuttlefish_mapping:mapping()]) -> [string()].
 generate(Mappings) ->
     lists:foldl(
@@ -341,6 +362,14 @@ generate_element_hidden_test() ->
     ?assertEqual([], cuttlefish_lager_test_backend:get_logs()),
     ok.
 
+shell_value_test() ->
+    Conf = file("test/shell_value.conf"),
+    ?assertEqual(lists:sort([
+             {["value1"],"42"},
+             {["value2"], "43"}
+        ]), lists:sort(Conf)),
+    ok.
+
 assert_no_output(Setting) ->
     Mapping = cuttlefish_mapping:parse(
                 {mapping,
diff --git a/test/shell_value.conf b/test/shell_value.conf
new file mode 100644
index 0000000..b1a2516
--- /dev/null
+++ b/test/shell_value.conf
@@ -0,0 +1,2 @@
+value1 = `cat value1`
+value2 = 43
diff --git a/test/value1 b/test/value1
new file mode 100644
index 0000000..d81cc07
--- /dev/null
+++ b/test/value1
@@ -0,0 +1 @@
+42