如何等待第一个命令完成? [英] how to wait for first command to finish?

问题描述

我正在用bash编写脚本，该脚本在内部调用了两个bash脚本.第一个脚本包含在后台运行的不同测试，第二个脚本打印第一个脚本的结果.

I am writing a script in bash, which is calling two bash scripts internally. Where first script includes different tests which runs in background and second script print results of first script.

当我一个接一个地运行这两个脚本时，有时，第二个脚本会在第一个脚本结束之前执行，这会打印错误的结果.

When I run these two scripts one after other, sometimes, second script get executed before first script ends Which prints wrong results.

我正在使用source命令运行两个脚本.有更好的建议吗?

I am running both scripts with source command. Any better suggestions?

source ../../st_new.sh -basedir $STRESS_PATH -instances $INSTANCES 
source ../../results.sh

推荐答案

Shell脚本，无论如何执行，都必须先执行一个命令.因此，您的代码将在st_new.sh的最后一条命令完成后执行results.sh.

Shell scripts, no matter how they are executed, execute one command after the other. So your code will execute results.sh after the last command of st_new.sh has finished.

现在有一个特殊的命令可以将其弄乱:&

Now there is a special command which messes this up: &

cmd &

表示:启动一个新的后台进程并在其中执行cmd.启动后台进程后，立即继续执行脚本中的下一个命令."

means: "Start a new background process and execute cmd in it. After starting the background process, immediately continue with the next command in the script."

这意味着&不会等待cmd正常工作.我的猜测是st_new.sh包含这样的命令.如果是这种情况，那么您需要修改脚本:

That means & doesn't wait for cmd to do it's work. My guess is that st_new.sh contains such a command. If that is the case, then you need to modify the script:

cmd &
BACK_PID=$!

这会将新后台进程的进程ID(PID)放入变量BACK_PID中.然后，您可以等待其结束:

This puts the process ID (PID) of the new background process in the variable BACK_PID. You can then wait for it to end:

while kill -0 $BACK_PID ; do
    echo "Process is still active..."
    sleep 1
    # You can add a timeout here if you want
done

或者，如果您不想仅进行任何特殊处理/输出

or, if you don't want any special handling/output simply

wait $BACK_PID

请注意，即使您省略了&，某些程序在运行时也会自动启动后台进程.查看文档，他们通常可以选择将其PID写入文件，或者您可以使用选项在前台运行它们，然后使用Shell的&命令获取PID.

Note that some programs automatically start a background process when you run them, even if you omit the &. Check the documentation, they often have an option to write their PID to a file or you can run them in the foreground with an option and then use the shell's & command instead to get the PID.

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