helpers: add "backtick" function for shell-like command

src/system/helpers.cpp

@@ -363,6 +363,23 @@ std::string find_executable(const char *name)
 	return "";
 }
 
+std::string backtick(std::string command)
+{
+	char *buf = NULL;
+	size_t n = 0;
+	pid_t pid;
+	FILE *p = my_popen(pid, command.c_str(), "r");
+	if (! p)
+		return "";
+	std::string out = "";
+	while (getline(&buf, &n, p) >= 0)
+		out.append(std::string(buf));
+	free(buf);
+	fclose(p);
+	waitpid(pid, NULL, 0);
+	return out;
+}
+
 std::string _getPathName(std::string &path, std::string sep)
 {
 	size_t pos = path.find_last_of(sep);

src/system/helpers.h

@@ -55,6 +55,8 @@ bool get_mem_usage(unsigned long &total, unsigned long &free);
 void mySleep(int sec);
 
 std::string find_executable(const char *name);
+/* basically what "foo=`command`" does in the shell */
+std::string backtick(std::string command);
 
 bool hdd_get_standby(const char * fname);
 void hdd_flush(const char * fname);