param: use PX4_INFO_RAW and add 'param show -q <param_name' command

src/systemcmds/param/param.cpp

@@ -40,6 +40,7 @@
  */
 
 #include <px4_config.h>
+#include <px4_log.h>
 #include <px4_module.h>
 #include <px4_posix.h>
 
@@ -72,7 +73,7 @@ enum COMPARE_OPERATOR {
 #ifdef __PX4_QURT
 #define PARAM_PRINT PX4_INFO
 #else
-#define PARAM_PRINT printf
+#define PARAM_PRINT PX4_INFO_RAW
 #endif
 
 static int 	do_save(const char *param_file_name);
@@ -80,6 +81,7 @@ static int	do_save_default();
 static int 	do_load(const char *param_file_name);
 static int	do_import(const char *param_file_name);
 static int	do_show(const char *search_string, bool only_changed);
+static int	do_show_quiet(const char *param_name);
 static int	do_show_index(const char *index, bool used_index);
 static void	do_show_print(void *arg, param_t param);
 static int	do_set(const char *name, const char *val, bool fail_on_not_found);
@@ -124,6 +126,7 @@ $ reboot
 
 	PRINT_MODULE_USAGE_COMMAND_DESCR("show", "Show parameter values");
 	PRINT_MODULE_USAGE_PARAM_FLAG('c', "Show only changed params", true);
+	PRINT_MODULE_USAGE_PARAM_FLAG('q', "quiet mode, print only param value (name needs to be exact)", true);
 	PRINT_MODULE_USAGE_ARG("<filter>", "Filter by param name (wildcard at end allowed, eg. sys_*)", true);
 
 	PRINT_MODULE_USAGE_COMMAND_DESCR("set", "Set parameter to a value");
@@ -213,6 +216,10 @@ param_main(int argc, char *argv[])
 						return do_show(nullptr, true);
 					}
 
+				} else if (!strcmp(argv[2], "-q")) {
+					if (argc >= 4) {
+						return do_show_quiet(argv[3]);
+					}
 				} else {
 					return do_show(argv[2], false);
 				}
@@ -419,6 +426,39 @@ do_show(const char *search_string, bool only_changed)
 
 	return 0;
 }
+static int
+do_show_quiet(const char *param_name)
+{
+	param_t param = param_find_no_notification(param_name);
+	int32_t ii;
+	float ff;
+	// Print only the param value (can be used in scripts)
+
+	if (param == PARAM_INVALID) {
+		return 1;
+	}
+
+	switch (param_type(param)) {
+	case PARAM_TYPE_INT32:
+		if (!param_get(param, &ii)) {
+			PARAM_PRINT("%ld", (long)ii);
+		}
+
+		break;
+
+	case PARAM_TYPE_FLOAT:
+		if (!param_get(param, &ff)) {
+			PARAM_PRINT("%4.4f", (double)ff);
+		}
+
+		break;
+
+	default:
+		return 1;
+	}
+
+	return 0;
+}
 
 static int
 do_find(const char *name)