Send DingTalk with shell and sign

ding_send.sh

#!/bin/bash

DING_SEC="<Your SEC Here>"
DING_URL="<Your Webhook Here>"

function hash_hmac {
    # hash_hmac sha256 data sec -binary
    old_lc_collate=$LC_COLLATE
    LC_COLLATE=C
    digest="$1"
    data="$2"
    key="$3"
    shift 3
    echo -n "$data" | openssl dgst "-$digest" -hmac "$key" "$@"
    LC_COLLATE=$old_lc_collate
}

urlencode() {
    # urlencode <string>
    old_lc_collate=$LC_COLLATE
    LC_COLLATE=C

    local length="${#1}"
    for ((i = 0; i < length; i++)); do
        local c="${1:$i:1}"
        case $c in
        [a-zA-Z0-9.~_-]) printf '%s' "$c" ;;
        *) printf '%%%02X' "'$c" ;;
        esac
    done

    LC_COLLATE=$old_lc_collate
}

escape_json_string() {
    JSON_TOPIC_RAW=$1
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//\\/\\\\} \
        JSON_TOPIC_RAW=${JSON_TOPIC_RAW//\//\\\/} # \
    # /
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//\'/\\\'} # ' (not strictly needed ?)
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//\"/\\\"} # "
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//   /\\t} # \t (tab)
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//
/\\\n}                                        # \n (newline)
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//^M/\\\r} # \r (carriage return)
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//^L/\\\f} # \f (form feed)
    JSON_TOPIC_RAW=${JSON_TOPIC_RAW//^H/\\\b} # \b (backspace)
    echo $JSON_TOPIC_RAW
}

send() {
    # send msg
    msg=$(escape_json_string "$1")

    DT=$(echo $(date +%s%N) / 1000000 | bc)
    data=$(echo -e "$DT\n$DING_SEC")
    SIGN=$(urlencode $(hash_hmac sha256 "$data" $DING_SEC -binary | base64))

    url="$DING_URL&sign=$SIGN&timestamp=$DT"
    POST_DATA=$(echo '{"msgtype": "text", "text": {"content": "' "$msg"'"}}')

    curl $url \
        -H 'Content-Type: application/json' -d "$POST_DATA"
}

send "$@"