signal

信号，kill只是个传递信号的作用
apue10
fig10_2_signal.c
造一个死循环，无限等待

我们必须区分系统调用和函数。当捕捉到某个信号时,被中断的是 内核中执行的系统调用。

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
static void sig_usr(int);   /* one handler for both signals */

int
main(void)
{
    if (signal(SIGUSR1, sig_usr) == SIG_ERR)
        printf("can't catch SIGUSR1");
    if (signal(SIGUSR2, sig_usr) == SIG_ERR)
        printf("can't catch SIGUSR2");
    for ( ; ; )
        pause();
}

static void
sig_usr(int signo)      /* argument is signal number */
{
    if (signo == SIGUSR1)
        printf("received SIGUSR1\n");
    else if (signo == SIGUSR2)
        printf("received SIGUSR2\n");
    else
        printf("received signal %d\n", signo);
}
~        

apple:mytest apple$ ./a.out &
[1] 1710
apple:mytest apple$ kill -USR1 1710
apple:mytest apple$ received SIGUSR1
kill -USR2 1710
received SIGUSR2
apple:mytest apple$

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