有没有办法让我的程序用更少的代码工作? [英] Is there a way to make my program work with less code?

问题描述

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.但只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.我尝试使用signal"而不是sigaction"，但我听说sigaction"比signal"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！

I wrote the following code for a school assignment - It compiles and prints all the correct messages. But just for my own curiosity, I would like to know if my code can be shorten and still works. I tried "signal" instead of "sigaction", but I heard that "sigaction" is strongly preferred over "signal". Also, this assignment requires 3 handlers. Can someone take a look and give me some tips? Thank you!

#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
"); //sig contains the signal number that was received
}

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

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

推荐答案

我想要一个单独的信号处理程序和一个带有 switch-case 的打印函数，用于每种信号消息:

I would like single signal handler and a print function with switch-case for each kind of signal message:

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
"); 
                   break;
     case SIGUSR2: printf("Caught SIGUSR2
"); 
                   break;
     case SIGINT: printf("Caught SIGINT, Exiting
");
                  exit(EXIT_SUCCESS);
     default: 
          printf("Some other signal");
  }
}

现在，检查 main 中的 flag，然后调用 print_msg(flag).
我的建议:避免在信号处理程序中使用 printf.

Now, Check the flag in your main, and call print_msg(flag).
My suggestion: 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.

In main(), register your single signal handler for each kind of signal.

// 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 文档，包括一个例子.

See the sigaction documentation, including an example.

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