bash:在后台运行多个命令，将输出存储在变量中

Question

如何并行运行一系列命令，并将它们的输出存储在变量中？

我试过:

output=`(echo -n "started "; sleep 2; echo "stopped") &`

echo "output before=$output"
wait
echo "output after=$output"

停顿了两秒钟，然后是:

output before=started stopped
output after=started stopped

我预计:

output before=
<2 seconds pause>
output after=started stopped

如何在后台运行一系列命令，并将它们的输出存储在变量中？

Answer 1

来自manual :

If a command is terminated by the control operator ‘&’, the shell executes the command asynchronously in a subshell. This is known as executing the command in the background. The shell does not wait for the command to finish, and the return status is 0 (true).

解决方法是将输出存储在文件中并从中读取。以下内容可能对您有用:

tempout=$(mktemp)
( echo -n "started "; sleep 2; echo "stopped" ) > "${tempout}" &
echo "output before=$(<$tempout)"
wait
echo "output after=$(<$tempout)"