recv函数的flag参数问题

[skyygl]

请问Unix下recv函数的flag参数在设置成MSG_WAITALL时,编译不过,提示:'MSG_WAITALL' was not declared in this scope,是什么原因?要不要包含什么头文件?

[kf701]

不支持，那个 flag 基本上没用。

[mhyx_2008]

[Quote=引用 1 楼 kf701 的回复:]
不支持，那个 flag 基本上没用。
[/Quote]
啊，可是我在一本书上看了说有这个参数的，它的意义是等待直到接收到指定长度的数据才返回，应该很有用才对啊！~

[windowsxp0925]

#include <sys/types.h>
#include <sys/socket.h>


MSG_WAITALL
This flag requests that the operation block until the full request is satisfied. However, the call may still return less
data than requested if a signal is caught, an error or disconnect occurs, or the next data to be received is of a different
type than that returned.

[windowsxp0925]

遇到此类问题man一下不就知道了？