[Linux] Kconfig中的depends on和select

config A
   depends on B
   select C

CONFIG_A能否開啟,取決於CONFIG_B是否開啟,

若CONFIG_A被開啟後，CONFIG_C也會自動被開啟.

make menuconfig → 讀取Kconfig →最後存到.config

[Linux] printk顯示關閉時間

時間開啟或關閉

開機後控制:
Enable dmesg timestamp
echo Y > /sys/module/printk/parameters/time

Disable dmesg timestamp
echo N > /sys/module/printk/parameters/time


make menuconfig設定:
CONFIG_PRINTK_TIME=y

[C] invoke在程式中的中文涵義

invoke: 在程式中自動被呼叫並執行

call: 手動呼叫並執行

"invoke" 在程式語言中該怎麼翻譯 (定義)

[Linux] Makefile Function

define funcName
@echo "pram1 = $(0)"
@echo "pram2 = $(1)"
@echo "pram3 = $(2)"
endef

all:
$(call funcName,hello 1,hello 2)

[C] JSON Library

安裝JSON函式庫(操作環境 ubuntu)
sudo apt install libjson-c-dev


範例1

int main()
{
	json_object *retObj_1 = NULL, *retObj_2 = NULL, *json_obj = NULL;
	int val_1, val_2;

	json_obj = json_object_new_object();

	/*Add object*/
	json_object_object_add(json_obj, "item1", json_object_new_int(123));
	json_object_object_add(json_obj, "item2", json_object_new_int(456));

	/*讀出json_obj內的所有key and value*/
	printf("%s\n", json_object_to_json_string(json_obj)); 
	//-> { "item1": 123, "item2": 456 }

	/*Get object, 下列兩種取到的object是一樣的*/
	retObj_1 = json_object_object_get(json_obj, "item1"); 	
	json_object_object_get_ex(json_obj, "item1", &retObj_2);
	//if retObj_1 = 0, item1 isn't existing

	val_1 = json_object_get_int (retObj_1);
	val_2 = json_object_get_int (retObj_2);
	printf(%d\n", json_object_get_int(val_1)); //-> 123
	printf("%d\n", json_object_get_int(val_2)); //-> 123
}

[Linux] iptables

filter table

• INPUT
• OUTPUT
• FORWARD

nat table

• PREROUTING
• POSTROUTING
• OUTPUT
• mangle table
• PREROUTING
• OUTPUT
• FORWARD
• INPUT
• POSTROUTING

raw table

• PREROUTING
• OUTPUT

[網頁] HTML, JavaSrcipt, CSS

<input type="text" v-model="message">

其中type的種類
button、checkbox、file、hidden、image、password、radio、reset、submit、text、color、date、datetime、datetime-local、email、month、number、range、search、tel、time、url、week

----------

JS函式

 

substring()

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substring