1 files changed, 63 insertions, 0 deletions
diff --git a/third_party/nix/src/nix/log.cc b/third_party/nix/src/nix/log.cc
new file mode 100644
index 000000000000..84207d8576ea
--- /dev/null
+++ b/third_party/nix/src/nix/log.cc
@@ -0,0 +1,63 @@
+#include <glog/logging.h>
+
+#include "libmain/common-args.hh"
+#include "libmain/shared.hh"
+#include "libstore/store-api.hh"
+#include "nix/command.hh"
+
+namespace nix {
+struct CmdLog final : InstallableCommand {
+  CmdLog() = default;
+
+  std::string name() override { return "log"; }
+
+  std::string description() override {
+    return "show the build log of the specified packages or paths, if "
+           "available";
+  }
+
+  Examples examples() override {
+    return {
+        Example{"To get the build log of GNU Hello:", "nix log nixpkgs.hello"},
+        Example{
+            "To get the build log of a specific path:",
+            "nix log "
+            "/nix/store/lmngj4wcm9rkv3w4dfhzhcyij3195hiq-thunderbird-52.2.1"},
+        Example{"To get a build log from a specific binary cache:",
+                "nix log --store https://cache.nixos.org nixpkgs.hello"},
+    };
+  }
+
+  void run(ref<Store> store) override {
+    settings.readOnlyMode = true;
+
+    auto subs = getDefaultSubstituters();
+
+    subs.push_front(store);
+
+    auto b = installable->toBuildable();
+
+    RunPager pager;
+    for (auto& sub : subs) {
+      auto log = !b.drvPath.empty() ? sub->getBuildLog(b.drvPath) : nullptr;
+      for (auto& output : b.outputs) {
+        if (log) {
+          break;
+        }
+        log = sub->getBuildLog(output.second);
+      }
+      if (!log) {
+        continue;
+      }
+      LOG(INFO) << "got build log for '" << installable->what() << "' from '"
+                << sub->getUri() << "'";
+      std::cout << *log;
+      return;
+    }
+
+    throw Error("build log of '%s' is not available", installable->what());
+  }
+};
+}  // namespace nix
+
+static nix::RegisterCommand r1(nix::make_ref<nix::CmdLog>());