问题描述
我工作的音频连接codeR CGI脚本，利用了libmp3lame。
我正在写在C / C ++的混合物。
I'm working on an audio encoder cgi script that utilises libmp3lame.I'm writing in a mixture of C/C++.
我计划有一个入口点的CGI，可以产卵，在后台运行多种编码过程。我需要的编码过程是异步的编码可能需要几个小时，但我需要的入口点CGI立即返回，以便浏览器可以继续对其业务。
I plan to have an entry-point cgi that can spawn multiple encoding processes that run in the background. I need the encoding processes to be asynchronous as encoding can take several hours but I need the entry-point cgi to return instantly so the browser can continue about its business.
我发现几个方案来解决这个（些完整/有些没有），但还有几件事情，我想澄清。
I have found several solutions for this (some complete/ some not) but there are still a few things I'd like to clear up.
解决方法1（简单）：入口点CGI是一个bash脚本，然后可以通过输出发送到在后台运行一个C ++程序CGI的/ dev / null的/ 2 /＆安培;> 1安培; （simples！但不是很优雅）。
Solution 1 (easiest): The entry-point cgi is a bash script which can then run a C++ process cgi in the background by sending the output to /dev/null/ 2/&>1& (simples! but not very elegant).
解决方案2：就像解决方案1，除了入口点cgi是C ++和使用系统（）运行在proc / s，并输出发送到/ dev / null的/ 2 /＆安培;> 1安培;试。
Solution 2: Much like solution 1, except the entry-point cgi is in C++ and uses system() to run the proc/s and send the output to /dev/null/ 2/&>1& again.
[提问]这工作很好，但我不知道，如果共享托管公司允许使用系统（）函数。这样的话？
[question] This works well but I'm not sure if shared hosting companies allow use of the system() function. Is this the case?
解决方案3（不完全）：我看着使用fork（）的/在pthread_create（）来派生独立的线程，这似乎更优雅，我可以留在C的领域唯一的问题存在：似乎父线程也不会退出，直到所有子线程回来了。
Solution 3 (incomplete): I've looked into using fork()/pthread_create() to spawn separate threads which seems more elegant as I can stay in the realms of C. The only problem being: It seems that the parent thread doesn't exit until all child threads have returned.
[提问]请问有什么办法让父线程退出，同时让子线程继续在后台运行。
[question] Is there any way to get the parent thread to exit whilst allowing child threads to continue in the background.
[思路]也许我可以在孩子PROC / s的输出发送到黑洞！我可以简单地重定向标准输出到/ dev / null的。如果是这样，我怎么做呢？
[idea] Maybe I can send the child proc/s output to the black hole! Can I simply redirect stdout to /dev/null. If so, how do I do this?
我希望这是有道理的人。我还是有点用C的东西一noob，所以我可能会丢失非常基本的概念（请怜悯！）。
I hope this makes sense to someone. I'm still a bit of a noob with C stuff so I may be missing very basic concepts (please have mercy!).
我会非常感激在这个问题上任何意见的。
I'd be very grateful of any advise on this matter.
在事先非常感谢，
乔希
推荐答案
您可能希望标准的Unix守护技术，涉及双叉：
You probably want the standard Unix daemon technique, involving a double fork:
void daemonize(void)
{
if (fork()) exit(0); // fork. parent exits.
setsid(); // become process group leader
if (fork()) _exit(0); // second parent exits.
chdir("/"); // just so we don't mysteriously prevent fs unmounts later
close(0); // close stdin, stdout, stderr.
close(1);
close(2);
}
看起来像现代的Linux机器有守护进程（）库函数presumably做同样的事情。
Looks like modern Linux machines have a daemon() library function that presumably does the same thing.
这有可能是第一个退出应 _exit ，但这code一直为我工作
It's possible that the first exit should be _exit, but this code has always worked for me.
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