slack-speak.sh

#!/bin/bash

# Fail script if any command fails
set -e

function usage {
  local script_name
  script_name=$(basename "$0")
  cat <<HELP
$script_name (options) <message>

Send a message to slack

Typical usage:
  echo "hello" | $script_name -n me -c #general -s subject

Options:
  -n: Nickname to speak as
  -c: Specific Slack channel to speak to
  -s: Title of the message
  -h: display this help
HELP
  exit 0
}

SLACK_CHANNEL="#general"
NICKNAME="grobot"
INCOMING_WEBHOOK="T0XXXXXXX/BYYYYYYY/vZZZZZZZZZZZZZZZZZZZZZ"
URL="https://hooks.slack.com/services/${INCOMING_WEBHOOK}"

while getopts "n:c:s:h" option; do
  case $option in
    c) SLACK_CHANNEL=$OPTARG ;;
    n) NICKNAME=$OPTARG ;;
    s) SUBJECT=$OPTARG ;;
    h) usage ;;
  esac
done

if [ -z "${SUBJECT}" ]; then
  echo -e "E: Missing subject to your message.\n"
  usage
  exit 1
fi

PAYLOAD='"channel": "'"${SLACK_CHANNEL}"'","username": "'"${NICKNAME}"'", "text": "'"${SUBJECT//\"/\\\"}"'"'

if grep -q "${NICKNAME}" "$(dirname "$0")/icon_nicknames"; then
 PAYLOAD=${PAYLOAD}', "icon_url": "https://www.example.com/icons/'${NICKNAME}'.png"'
fi

text=""
while IFS= read line; do
  text="$text\n${line//\"/\\\"}"
done

ATTACHMENTS='[{"text": "'"$text"'", "fallback": "'"$text"'"}]'
FORM_DATA='{'"$PAYLOAD"', "attachments": '"$ATTACHMENTS"'}'

curl -s -d "$FORM_DATA" "$URL"
printf "\n"