/*********************************************************************************
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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: fork.c
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* Description: This file is fork() example program.
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*
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* Version: 1.0.0(10/27/2025)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "10/27/2025 10:39:48 AM"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <string.h>
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int main(void)
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{
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int var = 10;
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pid_t pid;
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printf("parent process pid[%d] running...\n", getpid() );
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printf("before fork: var=%d, addr=%p\n", var, &var);
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printf("\n");
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pid = fork();
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if (pid < 0)
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{
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printf("fork() create child process failure: %s\n", strerror(errno));
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exit(1);
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}
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else if (pid == 0)
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{
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printf("child process pid[%d] running, parent pid is [%d]\n", getpid(), getppid());
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var = 20; /* 子进程修改变量 */
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printf("child process space: var=%d, addr=%p\n", var, &var);
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}
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else if( pid > 0 )
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{
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sleep(1); /* 父进程等待片刻，让子进程先执行 */
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printf("parent process pid[%d] running, child pid is [%d]\n", getpid(), pid);
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printf("parent process space: var=%d, addr=%p\n", var, &var);
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}
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printf("process pid[%d] exit\n\n", getpid());
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return 0;
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}
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