ref: a67a54fe25082be487fb60edd815181e5d949d1c
dir: /sys/src/libc/port/hangup.c/
#include <u.h>
#include <libc.h>
#include <ctype.h>
/*
 *  force a connection to hangup
 */
int
hangup(int ctl)
{
	return write(ctl, "hangup", sizeof("hangup")-1) != sizeof("hangup")-1;
}