C中父进程向子进程发送信号

我的子进程无法开始工作。我需要传递信号并执行readUsual功能。

这是一小段代码：

int main()
{
    pid_t pid2 = fork(); 
    if (pid2 < 0) 
        printf("Can't create child process\n");
    else if (pid2==0)
    {
        //this block never execute
        printf("Process2, pid=%d\n",getpid());
        signal(SIGUSR1,readUsual); 
    }
    else 
    {
        kill(pid2,SIGUSR1);
        printf("%s\n","Proccess1 end");
        for(;;);
    }

return 0;
}

您需要以某种方式添加同步，或者调用signal()在你之前fork().

使用您当前的代码，您无法确保子进程调用signal()在它接收到信号之前。在处理信号的指令之前接收信号将停止子进程。

Example:

#include <stdio.h>

#include <sys/types.h>
#include <signal.h>
#include <unistd.h>

static int received = 0;

void readUsual(int sig)
{
    if (sig == SIGUSR1)
    {
        received = 1;
    }
}

int main()
{
    signal(SIGUSR1,readUsual);

    pid_t pid2 = fork(); 
    if (pid2 < 0)
        printf("Can't create child process\n");
    else if (pid2==0)
    {
        printf("Process2, pid=%d\n",getpid());
        while (!received)
            ;
        printf("SIGUSR1 received.\n");
    }
    else 
    {
        kill(pid2,SIGUSR1);
        printf("%s\n","Proccess1 end");
        while (1)
            ;
    }

    return 0;
}

此代码的输出示例：

Process1 end
Process2, pid=1397
SIGUSR1 received