Run multiple curl commands in parallel

I have the following shell script. The issue is that I want to run the transactions parallel/concurrently without waiting for one request to finish to go to the next request. For example if I make 20 requests, I want them to be executed at the same time.

for ((request=1;request<=20;request++))
do
    for ((x=1;x<=20;x++))
    do
        time curl -X POST --header "http://localhost:5000/example"
    done
done

Any guide?

Solution 1:

Using xargs -P option, you can run any command in parallel:

xargs -I % -P 8 curl -X POST --header "http://localhost:5000/example" \
< <(printf '%s\n' {1..400})

This will run give curl command 400 times with max 8 jobs in parallel.

Solution 2:

You can use xargs with -P option to run any command in parallel:

seq 1 200 | xargs -n1 -P10  curl "http://localhost:5000/example"

This will run curl command 200 times with max 10 jobs in parallel.