Post a message to a Slack channel

slackpost

#!/bin/bash

# Usage: slackpost <token> <channel> <message>

# Enter the name of your slack host here - the thing that appears in your URL:
# https://slackhost.slack.com/
slackhost=PUT_YOUR_HOST_HERE

token=$1

if [[ $token == "" ]]
then
        echo "No token specified"
        exit 1
fi

shift
channel=$1
if [[ $channel == "" ]]
then
        echo "No channel specified"
        exit 1
fi

shift

text=$*

if [[ $text == "" ]]
then
        echo "No text specified"
        exit 1
fi

escapedText=$(echo $text | sed 's/"/\"/g' | sed "s/'/\'/g" )
json="{\"channel\": \"#$channel\", \"text\": \"$escapedText\"}"

curl -s -d "payload=$json" "https://$slackhost.slack.com/services/hooks/incoming-webhook?token=$token"

Don't add the payload key before json variable.
And add the token in the headers.

curl -v \
	-H 'Content-Type:application/json; charset=utf-8' \
	-H 'Authorization: Bearer xoxp-XXXXXX-XXXX-XXXXXXXX \
	--data "$json" \
	"$slackwebhook"