基于信号量实现linux平台守护进程

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <string>
#include <algorithm>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/sem.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pthread.h>
#include <semaphore.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <dirent.h>

using namespace std;
#define  WAIT_TIME_OUT              3

//根据进程名称获取进程id，然后根据进程id关闭进程
//ProcName:进程名称

int close_pid_by_name(string ProcName)
{
	DIR				*dir;	// 目录
	struct dirent	*d;		// 目录结构体
	pid_t			pid;	// 进程id
	char			*s;
	string			strpath, strpname;
	int pnlen, status;
	
	pnlen = ProcName.length();
	
	/* Open the /proc directory. */
	dir = opendir("/proc");
	if (!dir)
	{
		return -1;
	}
	
	// 遍历"/proc"目录
	while ((d = readdir(dir)) != NULL) {
		char exe[PATH_MAX + 1];
		char path[PATH_MAX + 1];
		int len;
		int namelen;
		// 判断是否是进程，每个进程按进程号分配文件夹 
		if ((pid = atoi(d->d_name)) == 0)
		    continue;
		
		snprintf(exe, sizeof(exe), "/proc/%s/exe", d->d_name);
		
		if ((len = readlink(exe, path, PATH_MAX)) < 0)
		    continue;
		path[len] = '\0';
		
		
		// 获取进程名称
		s = strrchr(path, '/');
		if (s == NULL)
		    continue;
		s++;
		
		strpname = s;
		
		// 进程名称匹配则杀死该进程
		namelen = strlen(s);
		if (namelen < pnlen)
		    continue;
		if (strpname.find(ProcName) != strpname.npos)
		{
		    kill(pid, SIGKILL);
		}
	}
	closedir(dir);
	return 0;
}

void daemon(string pname)
{
	// 创建信号量
	sem_t* psem = sem_open("/Name_Semphore", O_CREAT | O_RDONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP, 1);
	if (psem == SEM_FAILED)
	{
	    return;
	}
	
	while (true)
	{
		struct timespec ts;
		clock_gettime(CLOCK_REALTIME, &ts);
		ts.tv_sec = ts.tv_sec + WAIT_TIME_OUT;
		int result1 = sem_timedwait(psem, &ts);
		if (result1 == -1)
		{
		
		    ts.tv_sec = ts.tv_sec + WAIT_TIME_OUT;
		    int result2 = sem_timedwait(psem, &ts);
		    if (result2 == -1)
		    {
		
		        close_pid_by_name(pname);
		        break;
		    }
		}
		usleep(1000);
	}
	
	return;
}

int main(int argc, char* argv[])
{
	if (argc != 2)
	{
	    printf("paras err\n");
	    return -1;
	}

	// 被守护进程的名
	std::string process_name = argv[1];
	pid_t pid;
	int i, fd;
	pid = fork();			// 第一步,创建新进程
	if (pid < 0)
	{
	    printf("fork err\n");// fork失败
	    exit(1);
	}
	else if (pid > 0)
	{
	    printf("main quit\n");// 主进程直接退出
	    exit(0);
	}
	else // 这里是守护进程的内容
	{
		printf("daemon\n");
		setsid();		//第二步，设置新的会话
		chdir("/tmp");	//第三步，改变工作路径
		umask(0);		//第四步，改变掩码
		
		//第五步 关闭所有描述符，(输出信息可以记录在系统日志，/var/log/syslog)
		int max_fd = sysconf(_SC_OPEN_MAX);
		for (i = 0;i < max_fd;i++)
		    close(i);
		daemon(process_name);
	}
}