signal

//signaltest.c
// 子线程阻塞，等待信号，然后输出字符串
// 主线程从键盘录入字符，给子线程发信号。
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <pthread.h>
#include <time.h>
pthread_t tid;
sigset_t set;
void myfunc()
{
    printf("hello\n");
}

static void* mythread(void *p)
{
    int signum;
    while(1){
        sigwait(&set,&signum);
        if(SIGUSR1 == signum)
        myfunc();
        if(SIGUSR2 == signum)
        {
            printf("I will sleep 2 second and exit\n");
            sleep(2);
            break;
        }
    }
}

int main()
{
    char tmp;
    void* status;
    sigemptyset(&set);
    sigaddset(&set,SIGUSR1);
    sigaddset(&set,SIGUSR2);
    sigprocmask(SIG_SETMASK,&set,NULL);
    
    pthread_create(&tid,NULL,mythread,NULL);
    while(1)
    {
        printf(":");
        scanf("%c",&tmp);
        if('a' == tmp)
        {
            pthread_kill(tid,SIGUSR1); //发送SIGUSR1，打印字符串。
        }    
        else if('q'==tmp)
        {
            pthread_kill(tid,SIGUSR2); //发出SIGUSR2信号，让线程退出，如果发送SIGKILL，线程将直接退出。
            pthread_join(tid,&status); //等待线程tid执行完毕，这里阻塞。
            printf("finish\n");
            break;
        }
        else
            continue; 
    } 

return 0;
}







#include <signal.h> 
#include <unistd.h> 
#include <stdio.h> 
void sigroutine(int dunno) { /* 信号处理例程，其中dunno将会得到信号的值 */ 
switch (dunno) { 
case 1: 
printf("Get a signal -- SIGHUP "); 
break; 
case 2: 
printf("Get a signal -- SIGINT "); 
break; 
case 3: 
printf("Get a signal -- SIGQUIT "); 
break; 
} 
return; 
} 

int main() { 
printf("process id is %d ",getpid()); 
signal(SIGHUP, sigroutine); //* 下面设置三个信号的处理方法 
signal(SIGINT, sigroutine); 
signal(SIGQUIT, sigroutine); 
for (;;) ; 
} 





#include <signal.h> 
#include <unistd.h> 
#include <stdio.h> 
#include <sys/time.h> 
int sec; 

void sigroutine(int signo) { 
    switch (signo) { 
        case SIGALRM: 
            printf("Catch a signal -- SIGALRM "); 
            break; 
        case SIGVTALRM: 
            printf("Catch a signal -- SIGVTALRM "); 
            break; 
    } 
    return; 
} 

int main() { 
    struct itimerval value,ovalue,value2; 
    sec = 5; 
    
    printf("process id is %d ",getpid()); 
    signal(SIGALRM, sigroutine); 
    signal(SIGVTALRM, sigroutine); 
    
    value.it_value.tv_sec = 1; 
    value.it_value.tv_usec = 0; 
    value.it_interval.tv_sec = 1; 
    value.it_interval.tv_usec = 0; 
    setitimer(ITIMER_REAL, &value, &ovalue); 
    
    value2.it_value.tv_sec = 0; 
    value2.it_value.tv_usec = 500000; 
    value2.it_interval.tv_sec = 0; 
    value2.it_interval.tv_usec = 500000; 
    setitimer(ITIMER_VIRTUAL, &value2, &ovalue); 
    
    for (;;) ; 
} 







#include <stdio.h>
#define SIG_DFL ((void(*)(int))0)
#define SIG_IGN ((void(*)(int))1)

int main()
{
 int a = (int)SIG_DFL;
 int b = (int)SIG_IGN;
 
 printf("a = %d\n",a);  //0
 printf("b = %d\n",b);  //1

 return 0;
}