注釋

• 使用系統調用fork()創建三個子進程；
• 各個子進程顯示和輸出一些提示信息和自己的進程標識符；
• 父進程顯示自己的進程ID和一些提示信息，然后調用waitpid()等待多個子進程結束，并在子進程結束后顯示輸出提示信息表示程序結束。

代碼

#include <iostream>
#include <unistd.h>
#include <cstdarg>
#include <wait.h>
#include "crypto_util.h"int get_file(const std::string file_name){size_t get_file_id = 0;std::cout << hsm::common::get_md5_digest_hex(file_name) << std::endl;get_file_id = strtol(reinterpret_cast<const char *>(hsm::common::get_md5_digest_hex(file_name).substr(0,7).c_str()), nullptr, 16);return get_file_id;
}
int tprintf(const char *fmt,...){va_list args;struct tm* t_struct;time_t t_sec;t_sec = time(nullptr);t_struct = localtime(&t_sec);printf("%02d:%02d:%02d:%5d|",t_struct->tm_hour,t_struct->tm_min,t_struct->tm_sec,getpid());va_start(args,fmt);return vprintf(fmt,args);
}
int main(void) {std::cout << "Start!" << std::endl;printf("Father progress,PID is %d.\n",getpid());pid_t pid1 = fork();if(pid1 == 0){printf("Children progress 1,PID is %d.\n",getpid());exit(1);printf("Children progress 1 over.\n");}pid_t pid2 = fork();if(pid2 == 0){printf("Children progress 2,PID is %d.\n",getpid());exit(1);printf("Children progress 1 over.\n");}pid_t pid3 = fork();if(pid3 == 0){printf("Children progress 3,PID is %d.\n",getpid());exit(1);printf("Children progress 1 over.\n");}else if (pid1 != -1 ){tprintf("Parent forked children process-- %d.\n",pid1);tprintf("Parent is waiting for child to exit.\n");waitpid(pid1,NULL,0);waitpid(pid2,NULL,0);waitpid(pid3,NULL,0);tprintf("Child Process had exited.\n");tprintf("Parent had exited.\n");} else{tprintf("Everything was done without error.\n");}return 0;
}

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