bash 使用 & 在后台重击不同的循环并等待
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bash different loops in background using & and wait
提问by fabioln79
I've taken a look to the related topics but I did not found an answer.
我查看了相关主题，但没有找到答案。
Here's my problem:
这是我的问题：
I'm trying to put these commands that I usually run NOT in a for loop into two separate for loops
我试图将这些通常不在 for 循环中运行的命令放入两个单独的 for 循环中
original commands:
原始命令：
command1 &
command2 &
wait
command 3
This obviously starts two commands in background and, after BOTH are finished, it starts the command 3
这显然在后台启动了两个命令，在 BOTH 完成后，它启动了命令 3
Now here there's my for loop script:
现在这是我的 for 循环脚本：
file1=directory1/*.txt
for i in $file1;
do
command1 ${i} > ${i}.test & # I know, it will generate files like ".txt.test". It's ok.
done &
file2=directory2/*.txt
for i2 in $file2;
do
command1 ${i2} > ${i2}.test &
done &
wait
command3
Now there is somethig wrong in my script because sometimes when is performing the command 3 I can find some jobs from command1 or command2 EVEN if I put the "wait".
现在我的脚本中有一些错误，因为有时在执行命令 3 时，即使我输入“等待”，我也可以从 command1 或 command2 中找到一些作业。
I've tried different option like the second "done" without &. I've tried also two wait..but everything I do...I mess up all the jobs :(
我尝试了不同的选项，比如没有 & 的第二个“完成”。我也试过两次等待......但我所做的一切......我把所有的工作都搞砸了:(
Where is my mistake (please...be polite :P)?
我的错误在哪里（请...礼貌：P）？
Thank you
谢谢
Fabio
法比奥
回答by Radi R
Save both "for" loops, but remove all "&" from them, as separate files:loop1,loop2. chmod a+rx loop1 loop2; and execute:
保存两个“for”循环，但从它们中删除所有“&”，作为单独的文件：loop1,loop2。chmod a+rx loop1 loop2; 并执行：
loop1 &
loop2 &
wait
command3
I don't know the behaviour of "done &", better don't use it.
Your code is executing everything at the same time. I am assumming that you want 2 threads.
我不知道“done &”的行为，最好不要使用它。
您的代码同时执行所有内容。我假设你想要 2 个线程。
Edit: Single script solution:
编辑：单脚本解决方案：
script1=`mktemp /tmp/.script.XXXXXX`;
cat >$script1 <<END
for i in directory1/*.txt; do
command1 ${i} > ${i}.test;
done
END
script2=`mktemp /tmp/.script.XXXXXX`;
cat >$script2 <<END
for i in directory2/*.txt; do
command1 ${i} > ${i}.test;
done
END
chmod u+rx $script1 $script2
$script1 &
$script2 &
wait;
command3
/bin/rm $script1 $script2
回答by errant.info
There is no need for you to put the ampersand (&) after each done, you can simply put it after each command and all jobs from both loops will be put into the background and a single wait will do the trick.
您无需在每次完成后放置与号 (&)，您只需将它放在每个命令之后，两个循环中的所有作业都将被置于后台，一次等待即可解决问题。
for i in $( seq 1 3 ); do
command1 "$i" > "$i.test" &
done
for i in $( seq 4 6 ); do
command2 "$i" > "$i.test" &
done
wait
command3
An alternative approach is to store the pid of each background process by making use of $!, like so
另一种方法是通过使用 来存储每个后台进程的 pid $!，就像这样
pid=""
command & pid="$pid $!"
wait $pid
