command to back-up/compact DB

src/cmd_compact.cpp

@@ -0,0 +1,30 @@
+#include <unistd.h>
+#include <stdio.h>
+
+#include <docopt.h>
+#include "golpe.h"
+
+
+static const char USAGE[] =
+R"(
+    Usage:
+      compact <output_file>
+)";
+
+
+void cmd_compact(const std::vector<std::string> &subArgs) {
+    std::map<std::string, docopt::value> args = docopt::docopt(USAGE, subArgs, true, "");
+
+    std::string outputFile = args["<output_file>"].asString();
+
+    if (outputFile == "-") {
+        env.copy_fd(1);
+    } else {
+        if (access(outputFile.c_str(), F_OK) == 0) throw herr("output file '", outputFile, "' exists, not overwriting");
+
+        auto *f = ::fopen(outputFile.c_str(), "w");
+        if (!f) throw herr("opening output file '", outputFile, "' failed: ", strerror(errno));
+
+        env.copy_fd(::fileno(f));
+    }
+}