# stdarg.h

`stdarg.h`定义于函数的可变参数相关的一些方法。

- va_list 类型
- va_start()
- va_arg()：获取当前参数
- va_end()。

va_copy()：it makes a copy of your va_list variable in the exact same state.
va_copy() can be useful if you need to scan ahead through the arguments but need to also remember your current place.

接受可变函数作为参数的一些方法。

- vprintf()
- vfprintf()
- vsprintf()
- vsnprintf()

```c
#include <stdio.h>
#include <stdarg.h>

int my_printf(int serial, const char *format, ...)
{
    va_list va;

    // Do my custom work
    printf("The serial number is: %d\n", serial);

    // Then pass the rest off to vprintf()
    va_start(va, format);
    int rv = vprintf(format, va);
    va_end(va);

    return rv;
}

int main(void)
{
    int x = 10;
    float y = 3.2;

    my_printf(3490, "x is %d, y is %f\n", x, y);
}
```