如何在后台执行多个 bash 函数但等待输出？
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How do you execute several bash functions in the background but wait for output?
提问by Kevin
I am trying to make a bash function to execute several web scrapes (using curl and such), and I want to have them all execute concurrently in the background, and all print their output to stdin. How is this possible?
我正在尝试制作一个 bash 函数来执行多个网页抓取（使用 curl 等），并且我想让它们都在后台同时执行，并且都将它们的输出打印到标准输入。这怎么可能？
回答by TrueY
It is an easy one! You can use &for this even for bashfunctions:
这是一个简单的！您&甚至可以将其用于bash函数：
#!/usr/bin/bash
x() { echo ==Solaris; sleep 1; echo ==East; sleep 1; echo ==Panta Rhei;}
x one&
x two&
echo Syrius; sleep 1
echo After Crying
Output:
输出：
=one=Solaris
Syrius
=two=Solaris
=one=East
=two=East
After Crying
Press ENTER or type command to continue
=one=Panta Rhei
=two=Panta Rhei
So xis running in the background and prints to stdout. The Press ENTER or type command to continuewas presented by vim(as I started the script from vim) and shows that the background xprocess finishes its job after the main script finished. If You want to wait until all the background processes finish You can use the $!to get the PID of the background processes and the built-in wait <PID>as a last function.
所以x在后台运行并打印到stdout. 在Press ENTER or type command to continue被提出的VIM（我开始从脚本VIM），并显示该背景x的主脚本完成后，过程完成其工作。如果您想等到所有后台进程完成，您可以使用$!来获取后台进程的 PID，并将内置wait <PID>作为最后一个函数。
回答by Kevin
For anyone else who comes along:
对于其他任何人：
Given the following:
鉴于以下情况：
function par() {
parallel sh -c ::: "sleep 1" "sleep 1" "sleep 1"
}
function seq() {
sleep 1
sleep 1
sleep 1
}
Timing both commands shows that the first function executes all at once while the second function waits for each command to be finished before moving on to the next:
对这两个命令进行计时显示，第一个函数同时执行，而第二个函数在继续执行下一个命令之前等待每个命令完成：
$ time par && time seq
real 0m1.215s
user 0m0.147s
sys 0m0.085s
real 0m3.028s
user 0m0.011s
sys 0m0.012s
Happiness!
幸福！
