Add redirect for stdout to a file

main.cpp

@@ -40,6 +40,7 @@ void PrintUsage() {
             << std::endl
             << "Options:" << std::endl
             << " --help                   Display this message" << std::endl
+            << " -o,--output              Print output to file. [default: stdout]" << std::endl
             << " -y,--yaml                Format output as YAML. [default: disabled]" << std::endl
             << " -v VERBOSITY             Specify output verbosity (YAML output "
                "only):"
@@ -80,6 +81,7 @@ void PrintUsage() {
 int main(int argn, char** argv) {
   ArgParser arg_parser;
   arg_parser.AddFlag("h", "help", "");
+  arg_parser.AddOptionString("o", "output", "");
   arg_parser.AddFlag("y", "yaml", "");
   arg_parser.AddOptionInt("v", "verbosity", "", 0);
   arg_parser.AddFlag("e", "entrypoint", "");
@@ -97,6 +99,12 @@ int main(int argn, char** argv) {
     return EXIT_SUCCESS;
   }
 
+  std::string output_file;
+  arg_parser.GetString("o", "output", &output_file);
+  if (!output_file.empty()) {
+    freopen(output_file.c_str(), "w", stdout);
+  }
+
   bool output_as_yaml = arg_parser.GetFlag("y", "yaml");
 
   int yaml_verbosity = 0;