linux守护进程示例程序

#include <stdio.h>#include <fcntl.h>#include <stdlib.h>#include <unistd.h>#include <pwd.h>#include <time.h>#include <signal.h>int daemon(int, int);char *daemon_log = "/u01/log/daemon.log";int add_log(char*, char*);void sig_handler(int);void restart_sleep(int);int is_daemon = 1;int is_root = 1;int main(){fprintf(stdout, "daemon start/n");int ret;//是否切换到普通用户if (!is_root) {if (getuid() == 0 || geteuid() == 0) {char *username = "flynetcn";struct passwd *pw;if ((pw = getpwnam(username)) == 0) {fprintf(stderr, "can't find the user %s/n", username);return 1;}if (setgid(pw->pw_gid) < 0 || setuid(pw->pw_uid) < 0) {fprintf(stderr, "failed to assume identity of user %s/n", username);return 1;}}}//防止僵死子进程struct sigaction sa, oldsa;sa.sa_handler = sig_handler;sigemptyset(&sa.sa_mask);sa.sa_flags = SA_RESTART;if (sigaction(SIGCHLD, &sa, &oldsa) == -1) {fprintf(stderr, "sigaction(SIGCHLD) error/n");return 1;}//切换到守护进程if (is_daemon) {ret = daemon(1, 0);if (ret == -1) {fprintf(stderr, "failed to daemon/n");return 1;}}/** * do something */int crontimers[3][2];//task 1crontimers[0][0] = 3;crontimers[0][1] = 6;//task 2crontimers[1][0] = -1;crontimers[1][1] = 6;//task 3crontimers[2][0] = -1;crontimers[2][1] = 36;//tasks commchar *croncomm[3];croncomm[0] = "echo task1 >> /dev/null 2>&1";croncomm[1] = "echo task2 >> /dev/null 2>&1";croncomm[2] = "echo task3 >> /dev/null 2>&1";char buf[1024];char tbuf[50];time_t timestamp;struct tm *now;int time_left;int cron_num;cron_num = sizeof(croncomm)/sizeof(char*);int hok, i;while (1) {timestamp = time(NULL);now = localtime(&timestamp);strftime(tbuf, 30, "%Y-%m-%d %H:%M:%S", now);//sprintf(buf, "%s ------/n", tbuf);add_log(buf, daemon_log);for (i=0; i<cron_num; i++) {hok=0;sprintf(buf, "task %d :/n", i);add_log(buf, daemon_log);if (crontimers[i][0]==-1 || now->tm_hour==crontimers[i][0]) {hok = 1;add_log("hok/n", daemon_log);} else {continue;}if (crontimers[i][1]==now->tm_min && croncomm[i]) {add_log("mok/n", daemon_log);sprintf(buf, "run %s/n", croncomm[i]);add_log(buf, daemon_log);ret = fork();if (ret == 0) {system(croncomm[i]);exit(0);}}}timestamp = time(NULL);now = localtime(&timestamp);time_left = 60 - now->tm_sec;restart_sleep(time_left);}/** * end */}int add_log(char *str, char *logfile){FILE *fp;if ((fp = fopen(logfile, "a")) == NULL) {return -1;}if (!(*str) || fputs(str, fp)==EOF) {fclose(fp);return -1;}fflush(fp);fclose(fp);return 0;}int daemon(int nochdir, int noclose){int fd, ret;ret = fork();switch (ret) {case -1: return -1;case 0: break;default: exit(0);}if (setsid() == -1)return -1;if (nochdir == 0) {if(chdir("/") != 0) {perror("chdir");return -1;}}if (noclose == 0 && (fd = open("/dev/null", O_RDWR, 0)) != -1) {if(dup2(fd, STDIN_FILENO) < 0) {perror("dup2 stdin");return -1;}if(dup2(fd, STDOUT_FILENO) < 0) {perror("dup2 stdout");return -1;}if(dup2(fd, STDERR_FILENO) < 0) {perror("dup2 stderr");return -1;}if (fd > STDERR_FILENO) {if(close(fd) < 0) {perror("close");return -1;}}}return 0;}void sig_handler(int sig){if (sig == SIGCHLD) { int status;pid_t pid;pid = wait(&status);}}//防止被信号中断void restart_sleep(int sec){ int left; left = sec; while (left > 0) { left = sleep(left); }}