在后台运行多个程序并检查它们的返回值

Question

假设我想一次运行几个（比如三个）程序，像这样

program1 & program2 & program3 &

如果我想知道它们pid's，我认为最好的方法是存储它们，像这样

program1 &
pid1=$!
program2 &
pid2=$!
...

但是现在，如果我想知道它们是否已经结束，如果是，它们返回了什么值呢？像这样的东西：

if [ program1 has ended ]; then
    do something with its return value
fi

任何帮助将不胜感激

Answer 1

一个简单的解决方案是将消息写入日志文件

比如说，对于程序 1，执行如下操作：

#!/bin/bash
.
.
your stuff
.
.
end_time==$(date)
echo "program1 ended at $end_time" > program1_log

另一个想法是创建一个空文件来标记进程结束

#!/bin/bash
.
.
your stuff
.
.
echo $? > /some/path/program1_ended #storing the exit value
#disadvantage is that you can't verify if intermediate commands failed.

然后检查做

   if [ -e /some/path/program1_ended ]
   then
   exit_status=$( </some/path/program1_ended )
   rm /some/path/program1_ended #Deleting the file, getting ready for next run
   .
   .
   Do something
   else
   echo "program1 has not ended yet"
  fi