Send discord webhook using curl

reminder.sh

#!/bin/sh

WEBHOOK_URL="put your url here"
PING="<@put your user id here>"
MESSAGE="$PING reminder"
JSON="{\"content\": \"$MESSAGE\"}"

curl -d "$JSON" -H "Content-Type: application/json" "$WEBHOOK_URL"

or you can do it simply by running

curl -X POST --data '{"content": "REPLACE THIS WITH YOUR MESSSAGE"}' --header "Content-Type:application/json" "REPLACE THIS WITH A WEBHOOK URL"