Question

我为学校作业编写了以下代码 - 它编译并打印所有正确的消息。但仅仅是出于我自己的好奇心，我想知道我的代码是否可以缩短并且仍然有效。我试过“信号”而不是“sigaction”，但我听说“sigaction”比“信号”更受欢迎。此外，此分配需要3个处理程序。有人可以看看并给我一些提示吗？谢谢！

#define _POSIX_SOURCE
#define _BSD_SOURCE

#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>

static void sigHandler_sigusr1(int sig)
{
    printf("Caught SIGUSR1\n"); //sig contains the signal number that was received
}

static void sigHandler_sigusr2(int sig)
{
    printf("Caught SIGUSR2\n");
}

static void sigHandler_sigint(int sig)
{
    printf("Caught SIGINT, Existing\n");
    exit(EXIT_SUCCESS);
}

int main(int argc, char *argv[])
{
    struct sigaction s1;
    struct sigaction s2;
    struct sigaction s3;
    struct sigaction t;

    s1.sa_handler = sigHandler_sigusr1;
    sigemptyset(&s1.sa_mask);
    s1.sa_flags = 0;

    s2.sa_handler = sigHandler_sigusr2;
    sigemptyset(&s2.sa_mask);
    s2.sa_flags = 0;

    s3.sa_handler = sigHandler_sigint;
    sigemptyset(&s3.sa_mask);
    s3.sa_flags = 0;

    sigaction(SIGUSR1, &s1, &t);
    sigaction(SIGUSR2, &s2, &t);
    sigaction(SIGINT, &s3, &t);

    kill(getpid(), SIGUSR1);
    kill(getpid(), SIGUSR2);
    kill(getpid(), SIGINT);

    return 0;
}

Answer 1

我希望单信号处理程序和带有switch-case的打印功能用于各种信号消息：

volatile sig_atomic_t flag = 0;
// single signal handler
static void sigHandler_sigusr(int sig_no){
    flag = sig_no;  
}

void print_msg(int message_no){
  switch(message_no){
     case SIGUSR1: printf("Caught SIGUSR1\n"); 
                   break;
     case SIGUSR2: printf("Caught SIGUSR2\n"); 
                   break;
     case SIGINT: printf("Caught SIGINT, Exiting\n");
                  exit(EXIT_SUCCESS);
     default: 
          printf("Some other signal");
  }
}

现在，检查主要内容中的flag，然后拨打print_msg(flag) 我的建议是：avoid using printf in a signal handler。

在main（）中，为每种信号注册单个信号处理程序。

// prepare struct 
struct sigaction sa;
sa.sa_handler = sigHandler_sigusr;
sa.sa_flags = SA_RESTART; // Restart functions if
                          // interrupted by handler 

/* // unComment if you wants to block 
   // some signals while one is executing. 
sigset_t set;
sigemptyset( &set );
sigaddset( &set, SIGUSR1 );
sigaddset( &set, SIGUSR2 );
sigaddset( &set, SIGINT );
sa.sa_mask = set;
*/ 
// Register signals 
sigaction( SIGUSR1, &act, NULL );
sigaction( SIGUSR2, &act, NULL );
sigaction( SIGINT, &act, NULL );

请参阅sigaction documentation，包括示例。

Answer 2

static void sigHandlers(int sig)
{
  if (sig == SIGINT)
    printf("Caught SIGINT, Existing\n");
  else if (sig == SIGUSR1)
    printf("Caught SIGUSR1\n");
  else //no need to switch since you have only 3 sig
    printf("Caught SIGUSR2\n");
  exit(EXIT_SUCCESS);
}

int main(int argc, char *argv[])
{
  struct sigaction s[4] = {0};

  s[0].sa_handler = sigHandlers;
  sigemptyset(&(s[0].sa_mask));

  memcpy(&s[1], s, sizeof(struct sigaction));
  memcpy(&s[2], s, sizeof(struct sigaction));

  sigaction(SIGUSR1, &s[0], &s[3]);
  sigaction(SIGUSR2, &s[1], &s[3]);
  sigaction(SIGINT, &s[2], &s[3]);

  kill(getpid(), SIGUSR1);
  kill(getpid(), SIGUSR2);
  kill(getpid(), SIGINT);

  return 0;
}

但我确定您可以使用#define

来减少代码

有没有办法让我的程序使用更少的代码？

2 个答案: