Linux bash：静默杀死后台函数进程
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bash: silently kill background function process
提问by rouble
shell gurus,
贝壳大师，
I have a bash shell script, in which I launch a background function, say foo(), to display a progress bar for a boring and long command:
我有一个 bash shell 脚本，我在其中启动了一个后台函数，比如说foo()，为一个无聊而冗长的命令显示一个进度条：
foo()
{
while [ 1 ]
do
#massively cool progress bar display code
sleep 1
done
}
foo &
foo_pid=$!
boring_and_long_command
kill $foo_pid >/dev/null 2>&1
sleep 10
now, when foodies, I see the following text:
现在，当foo死亡时，我看到以下文字：
/home/user/script: line XXX: 30290 Killed foo
This totally destroys the awesomeness of my, otherwise massively cool, progress bar display.
这完全破坏了我的，否则非常酷的进度条显示的惊人之处。
How do I get rid of this message?
我如何摆脱这个消息？
采纳答案by Mark Edgar
kill $foo_pid
wait $foo_pid 2>/dev/null
BTW, I don't know about your massively cool progress bar, but have you seen Pipe Viewer (pv)? http://www.ivarch.com/programs/pv.shtml
顺便说一句，我不知道你的非常酷的进度条，但是你见过 Pipe Viewer (pv) 吗？ http://www.ivarch.com/programs/pv.shtml
回答by rouble
Try to replace your line kill $foo_pid >/dev/null 2>&1with the line:
尝试kill $foo_pid >/dev/null 2>&1用以下行替换您的行：
(kill $foo_pid 2>&1) >/dev/null
Update:
更新：
This answer is not correct for the reason explained by @mklement0 in his comment:
由于@mklement0 在他的评论中解释的原因，这个答案是不正确的：
The reason this answer isn't effective with background jobs is that Bash itself asynchronously, after the kill command has completed, outputs a status message about the killed job, which you cannot suppress directly - unless you use wait, as in the accepted answer.
这个答案对后台作业无效的原因是 Bash 本身异步地，在 kill 命令完成后，输出关于被杀死的作业的状态消息，你不能直接抑制 - 除非你使用等待，如接受的答案。
回答by rouble
This "hack" seems to work:
这个“黑客”似乎有效：
# Some trickery to hide killed message
exec 3>&2 # 3 is now a copy of 2
exec 2> /dev/null # 2 now points to /dev/null
kill $foo_pid >/dev/null 2>&1
sleep 1 # sleep to wait for process to die
exec 2>&3 # restore stderr to saved
exec 3>&- # close saved version
and it was inspired from here. World order has been restored.
它的灵感来自这里。世界秩序已经恢复。
回答by jilles
Add at the start of the function:
在函数的开头添加：
trap 'exit 0' TERM
回答by bbbco
This is a solution I came up with for a similar problem (wanted to display a timestamp during long running processes). This implements a killsub function that allows you to kill any subshell quietly as long as you know the pid. Note, that the trap instructions are important to include: in case the script is interrupted, the subshell will not continue to run.
这是我针对类似问题提出的解决方案（希望在长时间运行的进程中显示时间戳）。这实现了一个 killsub 函数，只要你知道 pid，它就允许你安静地杀死任何子 shell。请注意，陷阱指令很重要，包括：如果脚本被中断，子shell 将不会继续运行。
foo()
{
while [ 1 ]
do
#massively cool progress bar display code
sleep 1
done
}
#Kills the sub process quietly
function killsub()
{
kill -9 2>/dev/null
wait 2>/dev/null
}
foo &
foo_pid=$!
#Add a trap incase of unexpected interruptions
trap 'killsub ${foo_pid}; exit' INT TERM EXIT
boring_and_long_command
#Kill foo after finished
killsub ${foo_pid}
#Reset trap
trap - INT TERM EXIT
回答by Mike Q
Another way to do it:
另一种方法：
func_terminate_service(){
[[ "$(pidof )" ]] && killall
sleep 2
[[ "$(pidof )" ]] && kill -9 "$(pidof )"
}
call it with
用它来称呼它
func_terminate_service "firefox"
回答by phily
Yet another way to disable job notifications is to put your command to be backgrounded in a sh -c 'cmd &'construct.
另一种禁用作业通知的方法是将您的命令置于sh -c 'cmd &'构造中。
#!/bin/bash
foo()
{
while [ 1 ]
do
sleep 1
done
}
#foo &
#foo_pid=$!
export -f foo
foo_pid=`sh -c 'foo & echo ${!}' | head -1`
# if shell does not support exporting functions (export -f foo)
#arg1='foo() { while [ 1 ]; do sleep 1; done; }'
#foo_pid=`sh -c 'eval ""; foo & echo ${!}' _ "$arg1" | head -1`
sleep 3
echo kill ${foo_pid}
kill ${foo_pid}
sleep 3
exit
回答by pix
Just came across this myself, and realised "disown" is what we are looking for.
我自己刚刚遇到了这个，并意识到“disown”是我们正在寻找的。
foo &
foo_pid=$!
disown
boring_and_long_command
kill $foo_pid
sleep 10
The death message is being printed because the process is still in the shells list of watched "jobs". The disown command will remove the most recently spawned process from this list so that no debug message will be generated when it is killed, even with SIGKILL (-9).
正在打印死亡消息，因为该进程仍在监视的“作业”的 shell 列表中。disown 命令将从该列表中删除最近产生的进程，这样即使使用 SIGKILL (-9) 也不会在它被杀死时生成调试消息。
