How to Daemonize in Linux

最新推荐文章于 2024-12-06 10:59:56 发布

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最新推荐文章于 2024-12-06 10:59:56 发布

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分类专栏：技术研究相关文章标签： daemonize c linux

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本文提供了一个简单的Daemon进程实现代码示例。通过fork和setsid等系统调用，该示例展示了如何创建一个后台运行的进程，并重定向其标准输入、输出和错误到/dev/null。

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转自http://www.itp.uzh.ch/~dpotter/howto/daemonize

简单易懂的daemonize实现代码：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

#define EXIT_SUCCESS 0
#define EXIT_FAILURE 1

static void daemonize(void)
{
	pid_t pid, sid;

	/* already a daemon */
	if (getppid() == 1) {
		return;
	}

	/* Fork off the parent process */
	pid = fork();
	if (pid < 0) {
		exit(EXIT_FAILURE);
	}
	/* If we got a good PID, then we can exit the parent process. */
	if (pid > 0) {
		exit(EXIT_SUCCESS);
	}

	/* At this point we are executing as the child process */

	/* Change the file mode mask */
	umask(0);

	/* Create a new SID for the child process */
	sid = setsid();
	if (sid < 0) {
		exit(EXIT_FAILURE);
	}

	/* Change the current working directory.  This prevents the current
	 *        directory from being locked; hence not being able to remove it. */
	if ((chdir("/")) < 0) {
		exit(EXIT_FAILURE);
	}

	/* Redirect standard files to /dev/null */
	freopen("/dev/null", "r", stdin);
	freopen("/dev/null", "w", stdout);
	freopen("/dev/null", "w", stderr);
}

int main(int argc, char **argv)
{
	daemonize();

	/* Now we are a daemon -- do the work for which we were paid */

	while (1) {
		sleep(1);
	}

	return 0;
}