分叉/多线程进程|巴什

问题描述

我想使我的code的部分更有效。我想使它叉关闭到多个进程，并让他们在执行一次次50/100的，而不是只一次。

I would like to make a section of my code more efficient. I'm thinking of making it fork off into multiple processes and have them execute 50/100 times at once, instead of just once.

例如（伪）：

for line in file;
do
foo;
foo2;
foo3;
done

我想这个循环多次运行。我知道这与派生来完成。难道是这个样子？

I would like this for loop to run multiple times. I know this can be done with forking. Would it look something like this?

while(x <= 50)
parent(child pid)
{
   fork child()
}
child
{
   do
   foo; foo2; foo3;
   done
   return child_pid()
}

还是我想这个错误的方式？

Or am I thinking about this the wrong way?

谢谢！

推荐答案

在的bash脚本（非交互）默认情况下禁用作业控制，所以你不能做的命令：工作，FG和BG

In bash scripts (non-interactive) by default JOB CONTROL is disabled so you can't do the the commands: job, fg, and bg.

下面是很适合我：

#!/bin/sh

set -m # Enable Job Control

for i in `seq 30`; do # start 30 jobs in parallel
  sleep 3 &
done

# Wait for all parallel jobs to finish
while [ 1 ]; do fg 2> /dev/null; [ $? == 1 ] && break; done

最后一行使用FG带来了后台作业到前台。它这样做是在一个循环，直到FG返回1（$？== 1），当其不再有任何更多的后台作业它。

The last line uses "fg" to bring a background job into the foreground. It does this in a loop until fg returns 1 ($? == 1), which it does when there are no longer any more background jobs.

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