一、进程等待的必要性
二、进程等待的方法和概念
三、阻塞与非阻塞等待
3.1进程的阻塞等待：
int main() { pid_t pid; pid = fork(); if(pid < 0){ printf("%s fork error\n",__FUNCTION__); return 1; } else if( pid == 0 ){ //child printf("child is run, pid is : %d\n",getpid()); sleep(5); exit(257); } else{ int status = 0; pid_t ret = waitpid(-1, &status, 0);//阻塞式等待，等待5S printf("this is test for wait\n"); if( WIFEXITED(status) && ret == pid ){ printf("wait child 5s success, child return code is :%d.\n",WEXITSTATUS(status)); }else{ printf("wait child failed, return.\n"); return 1; } } return 0; }3.2进程的非阻塞等待：
#include <stdio.h> #include <stdlib.h> #include <sys/wait.h> #include <unistd.h> #include <vector> typedef void (*handler_t)(); // 函数指针类型 std::vector<handler_t> handlers; // 函数指针数组 void fun_one() { printf("这是⼀个临时任务1\n"); } void fun_two() { printf("这是⼀个临时任务2\n"); } void Load() { handlers.push_back(fun_one); handlers.push_back(fun_two); } void handler() { if (handlers.empty()) Load(); for (auto iter : handlers) iter(); } int main() { pid_t pid; pid = fork(); if (pid < 0) { printf("%s fork error\n", __FUNCTION__); return 1; } else if (pid == 0) { // child printf("child is run, pid is : %d\n", getpid()); sleep(5); exit(1); } else { int status = 0; pid_t ret = 0; do { ret = waitpid(-1, &status, WNOHANG); // ⾮阻塞式等待 if (ret == 0) { printf("child is running\n"); } handler(); } while (ret == 0); if (WIFEXITED(status) && ret == pid) { printf("wait child 5s success, child return code is :%d.\n", WEXITSTATUS(status)); } else { printf("wait child failed, return.\n"); return 1; } } return 0; }
