Add "nix show-config" command

This dumps the entire Nix configuration, including all options that
have default values.

1 files changed, 43 insertions, 0 deletions

diff --git a/src/nix/show-config.cc b/src/nix/show-config.cc
new file mode 100644
index 0000000000..ba39e2bb29
--- /dev/null
+++ b/src/nix/show-config.cc
@@ -0,0 +1,43 @@
+#include "command.hh"
+#include "common-args.hh"
+#include "installables.hh"
+#include "shared.hh"
+#include "store-api.hh"
+#include "json.hh"
+
+using namespace nix;
+
+struct CmdShowConfig : Command
+{
+    bool json = false;
+
+    CmdShowConfig()
+    {
+        mkFlag(0, "json", "produce JSON output", &json);
+    }
+
+    std::string name() override
+    {
+        return "show-config";
+    }
+
+    std::string description() override
+    {
+        return "show the Nix configuration";
+    }
+
+    void run() override
+    {
+        if (json) {
+            // FIXME: use appropriate JSON types (bool, ints, etc).
+            JSONObject jsonObj(std::cout, true);
+            for (auto & s : settings.getSettings())
+                jsonObj.attr(s.first, s.second);
+        } else {
+            for (auto & s : settings.getSettings())
+                std::cout << s.first + " = " + s.second + "\n";
+        }
+    }
+};
+
+static RegisterCommand r1(make_ref<CmdShowConfig>());