在命令运行时执行bash循环 [英] executing bash loop while command is running

问题描述

我想构建一个执行命令并同时执行其他任务的bash脚本，如果脚本被杀死，则有可能杀死该命令.说，执行一个大文件的cp，同时打印自复制开始以来经过的时间，但是如果脚本被杀死，它也会杀死副本. 我不想要使用rsync，原因有两个:1)运行缓慢，2)我想学习如何做，这可能会很有用. 我试过了:

I want to build a bash script that executes a command and in the meanwhile performs other stuff, with the possibility of killing the command if the script is killed. Say, executes a cp of a large file and in the meanwhile prints the elapsed time since copy started, but if the script is killed it kills also the copy. I don't want to use rsync, for 2 reasons: 1) is slow and 2) I want to learn how to do it, it could be useful. I tried this:

until cp SOURCE DEST
do
#evaluates time, stuff, commands, file dimensions, not important now
#and echoes something
done

，但它不执行do - done块，因为它正在等待副本结束.你能建议点什么吗?

but it doesn't execute the do - done block, as it is waiting that the copy ends. Could you please suggest something?

推荐答案

until与while相反.这与运行另一个命令时的工作无关.为此，您需要使用&在后台运行任务.

until is the opposite of while. It's nothing to do with doing stuff while another command runs. For that you need to run your task in the background with &.

cp SOURCE DEST &
pid=$!

# If this script is killed, kill the `cp'.
trap "kill $pid 2> /dev/null" EXIT

# While copy is running...
while kill -0 $pid 2> /dev/null; do
    # Do stuff
    ...
    sleep 1
done

# Disable the trap on a normal exit.
trap - EXIT

kill -0检查进程是否正在运行.注意，顾名思义，它实际上并没有发出信号并杀死它.至少没有信号0.

kill -0 checks if a process is running. Note that it doesn't actually signal the process and kill it, as the name might suggest. Not with signal 0, at least.

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