信號發送(sigqueue)和接收(sigaction)

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>



void handle(int signum, siginfo_t *info, void *p);

int main(void)
{
    pid_t fpid;

    union sigval value;     // 待發送的附加信息

    value.sival_int = 1942;

    struct sigaction act;   // 結構體中含接收到的信號和附加信息的處理函數(handle)

    act.sa_sigaction = handle;  // 處理函數(handle)
    act.sa_flags = SA_SIGINFO;  // 此成員爲SA_SIGINFO時纔會接受sigqueue發送的信號

    fpid = fork();

    if (fpid == -1) {
        perror("MSG");
    }


    if (fpid == 0) {
        sigqueue(getppid(), SIGINT, value);     // 發送信號(SIGINT)和附加信息(value)給父進程
        exit(0);
    }

    sigaction(SIGINT, &act, NULL);

    for(;;) {
        sleep(1);
    }

    return 0;
}

void handle(int signum, siginfo_t *info, void *p)
{
    int num = 0;
    num = info->si_value.sival_int;

    printf("recv value %d\n", num);
    printf("recv signal %d\n", signum);
}

/* 
    上面用到的系統調用如下：通過man手冊都能查到

    int sigqueue(pid_t pid, int sig, const union sigval value);

           union sigval {
               int   sival_int;
               void *sival_ptr;
           };

   int sigaction(int signum, const struct sigaction *act, 
                struct sigaction *oldact);
       struct sigaction {
           void     (*sa_handler)(int);
           void     (*sa_sigaction)(int, siginfo_t *, void *);
           sigset_t   sa_mask;
           int        sa_flags;
           void     (*sa_restorer)(void);
       };

       siginfo_t {
       int      si_signo;    /* Signal number *
       int      si_errno;    /* An errno value *
       int      si_code;     /* Signal code *
       int      si_trapno;   /* Trap number that caused
                                hardware-generated signal
                                (unused on most architectures) *
       pid_t    si_pid;      /* Sending process ID *
       uid_t    si_uid;      /* Real user ID of sending process *
       int      si_status;   /* Exit value or signal *
       clock_t  si_utime;    /* User time consumed *
       clock_t  si_stime;    /* System time consumed *
       sigval_t si_value;    /* Signal value *
       int      si_int;      /* POSIX.1b signal *
       void    *si_ptr;      /* POSIX.1b signal *
       int      si_overrun;  /* Timer overrun count; POSIX.1b timers *
       int      si_timerid;  /* Timer ID; POSIX.1b timers *
       void    *si_addr;     /* Memory location which caused fault *
       int      si_band;     /* Band event *
       int      si_fd;       /* File descriptor *
           }
*/