如何退出子shell [英] How to exit a Subshell

问题描述

基本上，我正在尝试退出包含循环的子外壳.这是代码: `

Basically, I am trying to exit a subshell that contains a loop. Here is the code: `

stop=0
(    # subshell start
    while true           # Loop start
    do
        sleep 1           # Wait a second
        echo 1 >> /tmp/output         # Add a line to a test file

        if [ $stop = 1 ]; then exit; fi         # This should exit the subshell if $stop is 1
    done   # Loop done

) |         # Do I need this pipe?

    while true   
    do
        zenity --title="Test" --ok-label="Stop" --cancel-label="Refresh" --text-info --filename=/tmp/output --font=couriernew        # This opens Zenity and shows the file.  It returns 0 when I click stop.

      if [ "$?" = 0 ]        # If Zenity returns 0, then
      then
         let stop=1       # This should close the subshell, and
         break        # This should close this loop
      fi
    done        # This loop end
    echo Done

这不起作用.它从不说完成.当我按下停止"按钮时，它只是关闭对话框，但继续写入文件.

This does not work. It never says Done. When I press Stop it just closes the dialog, but keeps writing to the file.

我需要能够将变量从子Shell传递到父Shell.但是，我需要继续写入文件并保持"Zenity"对话框出现.我该怎么办?

I need to be able to pass a variable from the subshell to the parent shell. However, I need to keep writing to the file and keep the Zenity dialog coming up. How would I do this?

推荐答案

生成子shell时，它将创建当前shell的子进程.这意味着，如果您在一个外壳中编辑变量，则该变量将不会反映在另一个外壳中，因为它们是不同的进程.我建议您将子外壳发送到后台，并使用$!获取其PID，然后在准备就绪时使用该PID杀死该子外壳.看起来像这样:

When you spawn a subshell, it creates a subprocess of the current shell. This means that if you edit a variable in one shell, it will not be reflected in the other, because they are different processes. I suggest you send the subshell to the background and use $! to get its PID, then use that PID to kill the subshell when you're ready. That would look like this:

(                               # subshell start
    while true                  # Loop start
    do
        sleep 1                 # Wait a second
        echo 1 >> /tmp/output   # Add a line to a test file
    done                        # Loop done

) &                             # Send the subshell to the background

SUBSHELL_PID=$!                 # Get the PID of the backgrounded subshell

while true   
do
  zenity --title="Test" --ok-label="Stop" --cancel-label="Refresh" --text-info --filename=/tmp/output --font=couriernew        # This opens Zenity and shows the file.  It returns 0 when I click stop.

  if [ "$?" = 0 ]               # If Zenity returns 0, then
  then
     kill $SUBSHELL_PID         # This will kill the subshell
     break                      # This should close this loop
  fi
done                            # This loop end

echo Done

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