Linux-C 进程通信之信号

野性酷女 2022-05-15 00:37 212阅读 0赞

### **Linux-C 进程通信之信号** ###

**一、简述**

**      记--进程之间使用信号进行通信。异步信号包含： 非实时信号 、实时信号。**

**       实时信号一定会响应，非实时信息号不一定会响应(可能会被忽略，或丢失)**

**     信号一般有以下设定：  
            1，捕捉    （收到某个信号，做指定的动作，而不是做默认的）  
            2，忽略    （收到某个信号，不做什么动作）  
            3，阻塞    （收到某个信号，先做完当前事情，然后在响应信号）  
            4，按照默认动作**

**     注：SIGKILL，SIGSTOP不能被捕捉**

**       关于信号的详细说明请参考man手册：man  7  signal。**

**二、signal()与kill()**

<table> signal()函数 
 <tbody> 
 <tr> 
 <td style="width:86px;">功能</td> 
 <td>简单的信号处理函数(信号捕捉函数)</td> 
 </tr> 
 <tr> 
 <td style="width:86px;">头文件</td> 
 <td>#include &lt;signal.h&gt;</td> 
 </tr> 
 <tr> 
 <td style="width:86px;">原型</td> 
 <td> typedef void (*sighandler_t)(int); //信号处理函数的 指针 sighandler_t signal(int signum, sighandler_t handler); </td> 
 </tr> 
 <tr> 
 <td style="width:86px;">参数</td> 
 <td> signum：要捕捉的信号 handler：处理方式 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;1、SIG_IGN：忽略这个信号 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2、SIG_DFL：按照默认动作执行这个信号 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;3、如果是一个函数，则是捕捉这个信号，收到这个信号的时候去执行这个函数。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; </td> 
 </tr> 
 <tr> 
 <td style="width:86px;">返回值</td> 
 <td> 成功：返回信号处理程序的先前值 出错：返回SIG_ERR，并设置errno </td> 
 </tr> 
 <tr> 
 <td style="width:86px;">备注</td> 
 <td>详细请查看man手册：man 2 signal (第7本也有)。可以配合kill()函数使用，kill()函数向某个进程发送某个指定的信号。</td> 
 </tr> 
 </tbody> 
</table>

测试代码1：捕捉中断信号(SIGINT)，接收到中断信号后，打印一句话"receive signal  %d\\n"。其中在终端按下Ctrl+c就发出终端信号，未捕捉之前，终端信号默认结束程序。

#include <stdio.h>
 #include <unistd.h>
 #include <signal.h>
 
 void SIGINT_handle(int sig_num)
 {
 	printf("reveice signal %d \n", sig_num);
 }
 
 int main(int argc, char argv[])
 {
 	int i;
 	signal(SIGINT, SIGINT_handle);
 
 	for(i=0; i<10; i++)
 	{
 		printf("i=%d \n", i);
 		sleep(1);
 	}
 	return 0;
 }

运行结果

捕捉终端信号：

![70][]

未捕捉的情况

![70 1][]

<table style="width:500px;"> kill()函数 
 <tbody> 
 <tr> 
 <td style="width:94px;">功能</td> 
 <td style="width:405px;">向一个进程发送信号</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">头文件</td> 
 <td style="width:405px;">#include &lt;sys/types.h&gt; #include &lt;signal.h&gt;</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">原型</td> 
 <td style="width:405px;">int kill(pid_t pid, int sig);</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">参数</td> 
 <td style="width:405px;"> pid：进程ID &nbsp;（process id） sig：要发送的信号 &nbsp;&nbsp; </td> 
 </tr> 
 <tr> 
 <td style="width:94px;">返回值</td> 
 <td style="width:405px;"> 成功：返回0 失败：返回-1，并设置error。 </td> 
 </tr> 
 <tr> 
 <td style="width:94px;">备注</td> 
 <td style="width:405px;">详细请查看man手册：man 2 kill</td> 
 </tr> 
 </tbody> 
</table>

测试代码2：使用kill()函数向signal程序发送SIGUSR1信号，a程序捕捉到之后打印一句话"receive signal  %d\\n"，然后退出。

kill.c文件

#include <stdio.h>
 #include <sys/types.h>
 #include <signal.h>
 
 int main(int argc, char *argv[])
 {
 	int pid, ret;
 	if(argc <2)
 	{
 		printf("arg error![./kill pid]\n");
 		return -1;
 	}
 	
 	sscanf( argv[1], "%d", &pid);
 	ret = kill(pid, SIGUSR1);
 	if(ret != 0 )
 	{
 		perror("kill SIGUSR1 error");
 		return -1;
 	}
 	printf("send SIGUSR1 to [pid]%d successful!\n", pid);
 
 	return 0;
 }

signal.c文件

#include <stdio.h>
 #include <unistd.h> //sleep()
 #include <signal.h> 
 #include <stdlib.h> //exit()
 
 void SIGUSR1_handle(int sig_num)
 {
 	printf("reveice signal %d \n", sig_num);
 	exit(0);
 }
 
 int main(int argc, char argv[])
 {
 	int i;
 	signal(SIGUSR1, SIGUSR1_handle);
 
 	for(i=0; i<30; i++)
 	{
 		printf("i=%d \n", i);
 		sleep(1);
 	}
 	return 0;
 }

运行结果：

![70 2][]

**三、sigprocmask()信号的阻塞**

**         信号的阻塞：在阻塞过程中，信号不会丢失，会被挂起，等解开阻塞的时候再响应。**

<table> sigprocmask()函数 
 <tbody> 
 <tr> 
 <td style="width:83px;">功能</td> 
 <td style="width:621px;">阻塞信号，延迟响应 。（检查并更改阻塞的信号）</td> 
 </tr> 
 <tr> 
 <td style="width:83px;">头文件</td> 
 <td style="width:621px;">#include &lt;signal.h&gt;</td> 
 </tr> 
 <tr> 
 <td style="width:83px;">原型</td> 
 <td style="width:621px;">int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);</td> 
 </tr> 
 <tr> 
 <td style="width:83px;">参数</td> 
 <td style="width:621px;"> how：对信号的操作（应用于信号集合中的所有函数） &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;SIG_BLOCK：添加信号集合里面的信号进行阻塞（原本的设置上添加设置） &nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;SIG_UNBLOCK：解除信号集合里面的信号的阻塞。 &nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;SIG_SETMASK：&nbsp;直接阻塞信号集合里面的信号，原本的设置直接被覆盖。 set：要设置的信号集合 &nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;int sigemptyset(sigset_t *set);//清空信号集合 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;int sigfillset(sigset_t *set);//将所有信号登记进集合里面 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;int sigaddset(sigset_t *set, int signum);//往集合里面添加signum信号 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; int sigdelset(sigset_t *set, int signum);//&nbsp;往集合里面删除signum信号 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; int sigismember(const sigset_t *set, int signum);//测试信号集合里面有无signum信号 oldset：用来保存旧的信号集合设置 &nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;如果这里是一个具体的指针，则将原本的设置保存在这里 &nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;如果是NULL则不保存。 </td> 
 </tr> 
 <tr> 
 <td style="width:83px;">返回值</td> 
 <td style="width:621px;"> 成功：返回0 失败：返回-1，并设置error </td> 
 </tr> 
 <tr> 
 <td style="width:83px;">备注</td> 
 <td style="width:621px;">在阻塞状态时，非实时信号可能会丢失</td> 
 </tr> 
 </tbody> 
</table>

例子：对中断信号、退出信号进行阻塞。然后向sigprocmask程序发送中断信号(Ctrl+c)、退出信号(Ctrl+\\)。那么sigprocmask程序收到信号后，不会立即响应，直到解除阻塞，才进行响应。其中，发送了两次中断信号（姑且命名为中断A,中断B），但是只响应了一次，是因为： 在某个时刻或阻塞时 接收到多个同一种非实时信号时，只会响应一次，其余丢弃，如果有一个已经开始响应了但是还没有结束，然后又来一个，那么这一个也会响应。

测试代码：

#include <stdio.h>
 #include <signal.h>
 #include <unistd.h>
 
 
 void signal_handle(int sig_num)
 {
 	printf("receive signal=%d\n", sig_num);
 
 }
 
 int main(void)
 {
 	int i;
 	sigset_t sigset;
 
 	signal(SIGINT, signal_handle);
 	signal(SIGQUIT, signal_handle);
 
 	sigemptyset(&sigset);//清空集合
 
 	sigaddset(&sigset, SIGINT);//将中断信号添加到 阻塞集合中
 	sigaddset(&sigset, SIGQUIT);//将退出信号添加到 阻塞集合中
 
 	sigprocmask(SIG_BLOCK, &sigset, NULL);//对信号进行阻塞
 
 	for(i=0; i<10; i++)
 	{
 		printf("i=%d \n", i);
 		sleep(1);
 	}
 
 	
 	sigprocmask(SIG_UNBLOCK, &sigset, NULL);//解开对信号的阻塞
 
 	printf("hello\n");
 
 	return 0;
 }

运行结果：

![70 3][]

**四、带数据的信号的发送与处理：**sigaction**()与sigqueue()**

<table> sigaction()函数 
 <tbody> 
 <tr> 
 <td style="width:94px;">功能</td> 
 <td>检查并改变信号动作（捕捉信号，指定处理动作）</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">头文件</td> 
 <td>#include &lt;signal.h&gt;</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">原型</td> 
 <td>int sigaction(int signum, const struct sigaction *act,struct sigaction *oldact);</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">参数</td> 
 <td> signum：捕捉的信号 act：信号动作结构体，用来登记对这个信号进行处理的动作。 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;struct sigaction&nbsp; &nbsp;&nbsp; &nbsp;{ &nbsp;&nbsp; &nbsp; &nbsp; void &nbsp; &nbsp; (*sa_handler)(int);&nbsp;&nbsp; &nbsp;//不带参数的信号处理函数，默认执行这个不带参数的信号处理函数 &nbsp;&nbsp; &nbsp; &nbsp; void &nbsp; &nbsp; (*sa_sigaction)(int, siginfo_t *, void *);//带参的信号处理函数，如果想要使能这个信号处理函数， &nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; //需要设置一下sa_flags为SA_SIGINFO &nbsp;&nbsp; &nbsp; &nbsp; sigset_t &nbsp; sa_mask;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;//信号阻塞设置 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;//1，在信号处理函数执行的过程当中阻塞掉指定的信号， &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;//指定的信号过来将会被挂起，等函数结束后再执行 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;//2，sigset_t信号集合类型，参照sigprocmask中sigset的使用方式。 &nbsp;&nbsp; &nbsp; &nbsp; int &nbsp; &nbsp; &nbsp; &nbsp;sa_flags;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;//信号的操作标识，例如设置使用的是带参信号处理函数，还是不带参数的 &nbsp;&nbsp; &nbsp; &nbsp; void &nbsp; &nbsp; (*sa_restorer)(void);&nbsp;&nbsp; &nbsp;//被遗弃的设置 &nbsp;&nbsp; &nbsp;}; oldact：用来保存原来的设置，如果是NULL则不保存。 </td> 
 </tr> 
 <tr> 
 <td style="width:94px;">返回值</td> 
 <td> 成功：返回0 失败：返回-1，并设置error </td> 
 </tr> 
 <tr> 
 <td style="width:94px;">备注</td> 
 <td>siginfo_t&nbsp; { &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_signo; &nbsp; &nbsp; /* Signal number */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_errno; &nbsp; &nbsp; /* An errno value */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_code; &nbsp; &nbsp; &nbsp;/* Signal code */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_trapno; &nbsp; &nbsp;/* Trap number that caused &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;hardware-generated signal &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(unused on most architectures) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;pid_t &nbsp; &nbsp;si_pid; &nbsp; &nbsp; &nbsp; /* Sending process ID */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;uid_t &nbsp; &nbsp;si_uid; &nbsp; &nbsp; &nbsp; /* Real user ID of sending process */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_status; &nbsp; &nbsp;/* Exit value or signal */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;clock_t &nbsp;si_utime; &nbsp; &nbsp; /* User time consumed */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;clock_t &nbsp;si_stime; &nbsp; &nbsp; /* System time consumed */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;sigval_t si_value; &nbsp; &nbsp; /* Signal value */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_int; &nbsp; &nbsp; &nbsp; /* POSIX.1b signal */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;void &nbsp; &nbsp;*si_ptr; &nbsp; &nbsp; &nbsp; /* POSIX.1b signal */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_overrun; &nbsp; /* Timer overrun count; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;POSIX.1b timers */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_timerid; &nbsp; /* Timer ID; POSIX.1b timers */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;void &nbsp; &nbsp;*si_addr; &nbsp; &nbsp; &nbsp;/* Memory location which caused fault */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;long &nbsp; &nbsp; si_band; &nbsp; &nbsp; &nbsp;/* Band event (was int in &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;glibc 2.3.2 and earlier) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_fd; &nbsp; &nbsp; &nbsp; &nbsp;/* File descriptor */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;short &nbsp; &nbsp;si_addr_lsb; &nbsp;/* Least significant bit of address &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(since Linux 2.6.32) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;void &nbsp; &nbsp;*si_lower; &nbsp; &nbsp; /* Lower bound when address violation &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;occurred (since Linux 3.19) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;void &nbsp; &nbsp;*si_upper; &nbsp; &nbsp; /* Upper bound when address violation &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;occurred (since Linux 3.19) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_pkey; &nbsp; &nbsp; &nbsp;/* Protection key on PTE that caused &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;fault (since Linux 4.6) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;void &nbsp; &nbsp;*si_call_addr; /* Address of system call instruction &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(since Linux 3.5) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int &nbsp; &nbsp; &nbsp;si_syscall; &nbsp; /* Number of attempted system call &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(since Linux 3.5) */ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;unsigned int si_arch; &nbsp;/* Architecture of attempted system call &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(since Linux 3.5) */ }；</td> 
 </tr> 
 </tbody> 
</table>

<table style="width:500px;"> sigqueue函数 
 <tbody> 
 <tr> 
 <td style="width:94px;">功能</td> 
 <td style="width:405px;">将信号和数据发送到指定进程</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">头文件</td> 
 <td style="width:405px;">#include &lt;signal.h&gt;</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">原型</td> 
 <td style="width:405px;">int sigqueue(pid_t pid, int sig, const union sigval value);</td> 
 </tr> 
 <tr> 
 <td style="width:94px;">参数</td> 
 <td style="width:405px;"> pid：进程ID sig：要发送的信号 value：附加数据 &nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;union sigval&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;{ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; int &nbsp; sival_int;//只附加一个int数据 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; void *sival_ptr;//附加更多数据(附加一个地址)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;//注：这是共用体、两者取其一 &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; </td> 
 </tr> 
 <tr> 
 <td style="width:94px;">返回值</td> 
 <td style="width:405px;"> 成功：返回0 失败：返回-1，并设置error </td> 
 </tr> 
 <tr> 
 <td style="width:94px;">备注</td> 
 <td style="width:405px;">跟sigaction结合使用</td> 
 </tr> 
 </tbody> 
</table>

例子：sigqueue程序向sigaction程序发送SIGUSR1信号，并附带int型数据123，sigaction捕捉到信号后，打印出信号发送方的PID和附加的数据，然后退出。

**       测试代码：**

**sigaction.c文件**

include <stdio.h>
 #include <signal.h>
 #include <unistd.h>
 #include <stdlib.h>
 
 
 void sigaction_handle(int signum, siginfo_t *info, void * ucontext)
 {
 
 	printf("info.si_pid=%d\n", info->si_pid);//打印信号发送方的pid
 	printf("info.si_int=%d\n", info->si_int);//打印信号发送方的附加数据
 	exit(0);
 
 }
 
 int main(void)
 {
 	int i;
 	struct sigaction act, oldact;
 	
 	act.sa_flags = SA_SIGINFO;//使用带参数的信号处理函数
 	act.sa_sigaction = sigaction_handle;
 
 //sigemptyset(&act.sa_mask);//清空原来集合
 	//sigfillset(&act.sa_mask);//将所有信号添加到集合
 
 	sigaction(SIGUSR1, &act, &oldact);//捕捉sigqueue发送的SIGUSR1信号
 
 	for(i=0; i<30; i++)
 	{
 		printf("i=%d\n", i);
 		sleep(1);
 	}
 	return 0;
 }

**sigqueue.c文件**

#include <stdio.h>
 #include <signal.h>
 
 #include <sys/types.h>//getpid()
 #include <unistd.h>
 
 int main(int argc, const char *argv[])
 {
 	if(argc < 2)
 	{
 		printf("arg error\n");
 		return -1;
 	}
 	union sigval value;
 	value.sival_int = 123;
 
 	int sig_num, pid;
 	
 	sscanf(argv[1], "%d", &pid);
 	sigqueue(pid, SIGUSR1, value);//向指定的pid发送SIGUSR1信号
 
 	printf("mypid=%d\n", getpid());//打印当前进程的ID号
 
 	return 0;
 }

**       运行结果： **

![70 4][]

**五、补充**

**  1、查看进程相关信息**

**        ps：查看进程状态   (一个瞬间的进程状态，静态)  
        top：“实时查看” ，按q退出    (实时动态显示)  
        pstree  树状查看  (可以看出所属子进程)   **

**        **![70 5][]

![70 6][]

![70 7][]

** 2、对某个进程发送信号**

**    kill  -s   指定发送一个信号      进程的pid  
    killall：指定一个应用程序名字去发送信号**

**    kill  -l   查看系统有什么信号 **

![70 8][]

**其中SIGKILL,SIGSTOP只能按照系统默认动作执行，不能捕捉，阻塞及忽略**

**前面31个是非实时信号：  
                1，每一个非实时信号对应一个信号名  
                2，每一个非实时信号基本上都会对应一个系统事件  
                3，信号有可能会丢失**

**后面的31个是实时信号：  
               1，信号不会丢失  
               2，优先级比非实时信号要高**

2、信号发送：  
    1，自己发给自己： raise()函数  
    2，发送信号给其他进程：  
              kill -s 信号 进程号  
              killall -s 信号 进程名字

3、信号的继承  
    1，信号初始化的设置是会被子进程继承的  
    2，信号的阻塞设置是会被子进程继承的  
    3，被挂起的信号是不会被子进程继承的

4、信号处理函数里面应该注意的地方：  
    1，不应该在信号处理函数里面操作全局变量（如果要操作，记得加锁）  
    2，应该注意一下一些函数调用是否安全，可以查看man 7 signal

5、测试所有信号的响应优先级

实时信号34-64：数字大的优先响应；

从1号信号开始发送

测试代码：

kill.c文件

#include <stdio.h>
 #include <signal.h>
 
 int main(int argc, const char *argv[])
 {
 	int signum, pid;
 	if(argc < 2)
 	{
 		printf("arg error\n");
 		return -1;
 	}
 	
 	sscanf(argv[1], "%d", &pid);
 	//向指定的进程发送所有的信号(不发送SIGKILL、SIGSTOP)
 	for(signum=1; signum<=64; signum++)
 	{
 		//系统没有32、33编号的信号，避免程序被kill掉或停止，不发送SIGKILL、SIGSTOP
 		if(signum == 33 || signum == 32 || signum == SIGKILL || signum == SIGSTOP)
 continue;
 		kill(pid, signum );
 	}
 
 	printf("send signal over\n");
 
 	return 0;
 }

signal.c文件

#include <stdio.h>
 #include <signal.h>
 #include <unistd.h>
 
 void signal_handle(int signum)
 {
 	printf("signal_handle signum=%d\n", signum);
 }
 
 int main(void)
 {
 	int signum, i;
 	struct sigaction act, oldact;
 
 	//捕捉所有的信号
 	for(signum = 1; signum<65; signum++)
 	{		
 		if(signum == 33 || signum == 32)
 			continue;
 
 		signal(signum, signal_handle);
 
 	}
 
 	printf("wait signal\n");	
 	//延时30秒，等待信号处理完毕
 	for(i=0; i<30; i++)
 	{
 		sleep(1);
 	}
 	
 	return 0;
 }

运行结果：

![70 9][]

signal_handle signum=64
    signal_handle signum=63
    signal_handle signum=62
    signal_handle signum=61
    signal_handle signum=60
    signal_handle signum=59
    signal_handle signum=58
    signal_handle signum=57
    signal_handle signum=56
    signal_handle signum=55
    signal_handle signum=54
    signal_handle signum=53
    signal_handle signum=52
    signal_handle signum=51
    signal_handle signum=50
    signal_handle signum=49
    signal_handle signum=48
    signal_handle signum=47
    signal_handle signum=46
    signal_handle signum=45
    signal_handle signum=44
    signal_handle signum=43
    signal_handle signum=42
    signal_handle signum=41
    signal_handle signum=40
    signal_handle signum=39
    signal_handle signum=38
    signal_handle signum=37
    signal_handle signum=36
    signal_handle signum=35
    signal_handle signum=34
    signal_handle signum=30
    signal_handle signum=29
    signal_handle signum=28
    signal_handle signum=27
    signal_handle signum=26
    signal_handle signum=25
    signal_handle signum=24
    signal_handle signum=23
    signal_handle signum=22
    signal_handle signum=21
    signal_handle signum=20
    signal_handle signum=17
    signal_handle signum=16
    signal_handle signum=15
    signal_handle signum=14
    signal_handle signum=13
    signal_handle signum=12
    signal_handle signum=10
    signal_handle signum=6
    signal_handle signum=3
    signal_handle signum=2
    signal_handle signum=1
    signal_handle signum=31
    signal_handle signum=11
    signal_handle signum=8
    signal_handle signum=7
    signal_handle signum=5
    signal_handle signum=4

================================================================================================

从64号开始发送

运行结果：

![70 10][]

[70]: /images/20220515/94a456c059554c50871fe1f4a5e6c2e9.png
[70 1]: /images/20220515/2278e01af57b49c68e7936fb81118f5a.png
[70 2]: /images/20220515/307167dbb93e4715ab12c32a6daa9005.png
[70 3]: /images/20220515/d84f625e594849d398777a8a50072635.png
[70 4]: /images/20220515/96c979afb9164a9999fa1a508d6a08e7.png
[70 5]: /images/20220515/33b040ce83444f7fa0565d8bd1d2a022.png
[70 6]: /images/20220515/3a11611ed1f74a918f95dd65c15e807d.png
[70 7]: /images/20220515/1a7f35244e084938b0131e0b0080f2ec.png
[70 8]: /images/20220515/a4adba272357406487935a94105fdb8c.png
[70 9]: /images/20220515/615615232c1348b296fc8a8834e309e9.png
[70 10]: /images/20220515/3a76740d0f634d76875667cc08bb0335.png