Send a message to a Slack Webhook

notify_slack.sh

#!/bin/bash 
set -e 

## Take in the Webhook URL from Slack and the actual message to send.
if [[ $# -ne 2 ]]; then
    ( >&2 echo "Usage $(basename "$0") WEBHOOK_URL MESSAGE" )
    exit 1
fi

WEBHOOK_URL=$1
MESSAGE=$2

## Using a heredoc means you can type unescaped quotes, use interpolation and even whitespace to indent!
PAYLOAD=$(cat <<EOF
{"text": "$MESSAGE"}
EOF
)

# Flags used:
## --silent - no annoying progress bar.
## --request - the HTTP verb.
## --header - Never send JSON without saying it's JSON!
## --data - the body.
curl --silent \
    --request POST \
    --header "Content-Type: application/json" \
    --data "$PAYLOAD" \
    "$WEBHOOK_URL"