system-cmd-fork added

ml_io.cpp

@@ -109,3 +109,32 @@ MlValue exec_system_cmd(const std::string &cmd) {
 
 	return std::vector<MlValue> { MlValue((long)cmd_retval), MlValue::string(cmd_output) };
 }
+
+
+MlValue exec_system_cmd_fork(const std::vector<std::string> &args) {
+	int pid = fork();
+	if (pid == 0) {
+	    // Child process, execute the command
+
+    	std::vector<char*> exec_args;
+		exec_args.reserve(args.size());
+
+	    for (auto const& a : args) 
+	        exec_args.emplace_back(const_cast<char*>(a.c_str()));
+
+    	exec_args.push_back(nullptr);	// exec must end with null
+
+    	execvp(args[0].c_str(), exec_args.data());
+
+		std::cerr << "execvp error: " << errno << ", " << strerror(errno) <<  std::endl;
+    	exit(1);	// indicate error, if here
+
+	} else if (pid > 0) {
+	    // Parent process, child process is now independent
+		return std::vector<MlValue> { MlValue((long)0), MlValue::string("") };
+
+	} else {
+	    // Fork error, still in parent process (there are no child process at this point)
+		return std::vector<MlValue> { MlValue((long)errno), MlValue::string(strerror(errno) ) };
+	}
+}