/*********************************************************************************
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* Copyright: (C) 2025 LingYun IoT System Studio
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* All rights reserved.
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*
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* Filename: signal.c
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* Description: This file is signal example program
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*
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* Version: 1.0.0(11/07/2025)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "11/07/2025 10:18:12 AM"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <signal.h>
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int g_child_stop = 0;
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int g_parent_run = 0;
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void sig_child(int signum)
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{
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if( SIGUSR1 == signum )
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{
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g_child_stop = 1;
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}
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}
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void sig_parent(int signum)
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{
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if( SIGUSR2 == signum )
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{
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g_parent_run = 1;
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}
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}
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int main(int argc, char **argv)
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{
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int pid;
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int wstatus;
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signal(SIGUSR1, sig_child);
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signal(SIGUSR2, sig_parent);
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if( (pid=fork()) < 0 )
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{
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printf("Create child process failure: %s\n", strerror(errno));
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return -2;
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}
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else if(pid == 0)
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{
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/* child process can do something first here */
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printf("Child process working...\n");
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sleep(1);
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printf("Child process done and send parent signal SIGUSR2\n");
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kill(getppid(), SIGUSR2);
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while( !g_child_stop )
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{
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sleep(1);
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}
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printf("Child process receive signal from parent and exit now\n");
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return 0;
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}
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printf("Parent hangs up to wait for signal from child\n");
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while( !g_parent_run )
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{
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sleep(1);
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}
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/* parent process can do something here */
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printf("Parent process working...\n");
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sleep(1);
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printf("Parent process done and send child signal SIGUSR1\n");
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kill(pid, SIGUSR1);
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/* parent wait child process exit */
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wait(&wstatus);
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printf("Parent process receive signal from child and exit now\n");
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return 0;
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}
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