1.缘起

这个系列会汇集一些临近deadline是最后补救措施，以备不时之需。面临项目交付时，经常会有一些或大或小的功能项点，甚至是bug无法做完。这个时候，就需要一些终极补救措施来应对这种不时之需。

第一个工具app_daemon是针对那些需要长周期运行，但是一些内存泄露或者别的资源释放问题迟迟无法解决的情形，它叫应用程序看护工具，实际运行效果是这样的：

[root@localhost app_daemon]# ./app_daemon ./test_app
real app runing....
real app quited
Application scheduling exited. Restarting in 5 seconds...
real app runing....
real app quited
Application scheduling exited. Restarting in 5 seconds...
real app runing....
real app quited
Application scheduling exited. Restarting in 5 seconds...

2.编码 

//usage: app_daemon <app_to_daemon's cmd_line> [param1 param2 param3...]
//build:gcc app_daemon.c -o app_daemon
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>void runWatchingAppAsSubApp(int argc, char *argv[]) {char new_cmd[2048] = {0};int i;int l;for(i=0; i<argc; ++i){l = strnlen(new_cmd, 2048);if(i==0){continue; //i==0 is itsself}else{snprintf(&new_cmd[l], sizeof(new_cmd)-l-1, "%s ", argv[i]);}// 替换为您的应用程序启动命令system(new_cmd);}
}int main(int argc, char *argv[]) {if(argc == 1){printf("Usage:%s <app_to_watch> [param1, param2...]\n", argv[0]);return 0;}while (1) {pid_t pid = fork();if (pid == 0) {// 子进程中运行应用程序runWatchingAppAsSubApp(argc, argv);exit(0);} else if (pid > 0) {// 等待应用程序退出int status;waitpid(pid, &status, 0);// 延时重启时间（单位：秒）int restart_delay = 5; // 5 秒printf("Application scheduling exited. Restarting in %d seconds...\n", restart_delay);sleep(restart_delay);} else {printf("Fork failed\n");return 1;}}return 0;
}

附录A 用于测试的一个桩应用

void main(void)
{printf("real app runing....\n");sleep(3);printf("real app quited\n");
}
~