bash Curl：不要等待响应
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Curl: don't wait for response
提问by tuxlu
I currently have a shell script which relies on a curl command like this:
我目前有一个 shell 脚本，它依赖于这样的 curl 命令：
curl --request POST -u name:pass -H "Content-Type: application/json"
--data "{data}" https://url.com --cacert ./my_crt
I don't need the response of the command, and this command is in a big for loop, so waiting for the responses take a lot of time.
我不需要命令的响应，而且这个命令在一个很大的for循环中，所以等待响应需要很多时间。
so, is there a way in bash to do exactly the same thing, but without waiting for the response?
那么，bash 中是否有一种方法可以做完全相同的事情，但无需等待响应？
回答by that other guy
If you have a large number of requests you want to issue quickly, and you don't care about the output, there are two things you should do:
如果你有大量的请求想要快速发出，并且你不关心输出，那么你应该做两件事：
- Do more requests with the same connection.
- 使用相同的连接执行更多请求。
For small requests, it's generally much faster to do 10 requests each on 1 connection, than 1 request each on 10 connections. For Henry's HTTP post test server, the difference is 2.5x:
对于小请求，通常在 1 个连接上分别执行 10 个请求比在 10 个连接上每个请求快得多。对于Henry的HTTP post test server，相差2.5x：
$ time for i in {1..10}; do
curl -F foo=bar https://posttestserver.com/post.php ;
done
Successfully dumped 1 post variables.
View it at http://www.posttestserver.com/data/2016/06/09/11.44.48536583865
Post body was 0 chars long.
(...)
real 0m2.429s
vs
对比
$ time {
array=();
for i in {1..10}; do
array+=(--next -F foo=bar https://posttestserver.com/post.php ) ;
done;
curl "${array[@]}";
}
Successfully dumped 1 post variables.
View it at http://www.posttestserver.com/data/2016/06/09/11.45.461371907842
(...)
real 0m1.079s
- Process at most a N connections in parallel, to avoid DoS'ing the host or your machine
- 最多并行处理 N 个连接，以避免对主机或您的机器进行 DoS
Here semfrom GNU parallel is limiting the number of parallel connections to 4. This is a better version of backgrounding and waiting, since it will always ensure full capacity.
这里sem来自 GNU parallel 将并行连接的数量限制为 4。这是后台和等待的更好版本，因为它始终确保满容量。
for i in {1..20}
do
sem -j 4 curl -F foo=bar https://posttestserver.com/post.php
done
sem --wait
The number of parallel requests you want depends on how beefy the host is. A realistic number could be 32+
您想要的并行请求数量取决于主机的强大程度。一个现实的数字可能是 32+
Combine the two strategies, and you should see a hefty speedup without DoS'ing yourself.
结合这两种策略，您应该会在不进行 DoS 的情况下看到显着的加速。
回答by razz
You could just background it with &and to prevent output you can redirect stdoutand stderrto to /dev/null.
你可以只将其与背景&，并防止你可以重定向输出stdout和stderr向/dev/null。
curl --request POST -u name:pass -H "Content-Type: application/json" \
--data "{data}" https://url.com --cacert ./my_crt > /dev/null 2>&1 &
