I started writing another post, but wound up writing a non-trivial script for working with Phoenix JSON APIs. That script is covered in this post. It is written for the FreeBSD Bourne shell, but it should be compatible with bash.

This post also serves as a getopts example. getopts was used instead of getopt because getopt does not support command line arguments that contain spaces.

Software Versions

$ date -u "+%Y-%m-%d %H:%M:%S +0000"
2016-03-19 00:55:41 +0000
$ uname -vm
FreeBSD 11.0-CURRENT #0 r296925: Wed Mar 16 20:53:04 JST 2016     root@mirage.sennue.com:/usr/obj/usr/src/sys/MIRAGE_KERNEL  amd64
$ mix hex.info
Hex:    0.11.3
Elixir: 1.2.3
OTP:    18.2.4
* snip *
$ mix phoenix.new -v
Phoenix v1.1.4


Create a new Phoenix project.

mix phoenix.new phoenix_service --no-brunch
cd phoenix_service
mix ecto.create

This example will use a JSON memo service.

mix phoenix.gen.json Memo memos title:string body:string

Revise the web/router.ex file. The “/api” scope needs to be uncommented and the “/memos” route needs to be added.

web/router.ex file

defmodule PhoenixService.Router do
  use PhoenixService.Web, :router

  pipeline :browser do
    plug :accepts, ["html"]
    plug :fetch_session
    plug :fetch_flash
    plug :protect_from_forgery
    plug :put_secure_browser_headers

  pipeline :api do
    plug :accepts, ["json"]

  scope "/", PhoenixService do
    pipe_through :browser # Use the default browser stack
    get "/", PageController, :index

  scope "/api", PhoenixService do
    pipe_through :api

    resources "/memos", MemoController, except: [:new, :edit]

Run the migration.

mix ecto.migrate

Tests should pass.

mix test

Running the Sample Project

Start the server.

mix phoenix.server

The following curl commands can be used to interact with the JSON API.

# POST new
curl -H 'Content-Type: application/json' -X POST -d '{"memo": {"title": "New Title", "body": "This is the new memo body."}}' http://localhost:4000/api/memos
# PATCH id 1
curl -H 'Content-Type: application/json' -X PATCH -d '{"memo": {"title": "Patched Title"}}' http://localhost:4000/api/memos/1
curl -H 'Content-Type: application/json' -X PATCH -d '{"memo": {"body": "Patched memo body."}}' http://localhost:4000/api/memos/1
# PUT id 1
curl -H 'Content-Type: application/json' -X PUT -d '{"memo": {"title": "Updated Title", "body": "Updated memo body."}}' http://localhost:4000/api/memos/1
# GET all
curl -H 'Content-Type: application/json' http://localhost:4000/api/memos
# GET id 1
curl -H 'Content-Type: application/json' http://localhost:4000/api/memos/1
# DELETE id 1
curl -H 'Content-Type: application/json' -X DELETE http://localhost:4000/api/memos/1

A script is easier to use if you need to make more than a couple of curl calls. It can also be extended to support authentication and everything else your API may need.

Create a script to GET, POST, PATCH, PUT and DELETE memos. Note that a Bourne Shell tutorial can be found here.



reset() {
  HEADERS="Content-Type: application/json"

usage() {
  echo "Usage:  ${0} [options]"
  echo "Options:"
  echo "  -o HOST : set URL host, defaults to \"${HOST}\""
  echo "  -s SCOPE : set URL scope, defaults to \"${SCOPE}\""
  echo "  -r ROUTE : set URL route, defaults to \"${ROUTE}\""
  echo "  -X METHOD : set HTTP method, defaults to \"${METHOD}\""
  echo "  -H HEADERS : set HTTP headers, defaults to \"${HEADERS}\""
  echo "  -i ID : set memo id, defaults to \"${ID}\""
  echo "  -t TITLE : set memo title, defaults to \"${TITLE}\""
  echo "  -b BODY : set memo body, defaults to \"${BODY}\""
  echo "  -h : display this help"
  echo "Examples:"
  echo "  ${0} -X GET"
  echo "  ${0} -X GET -i 7"
  echo "  ${0} -X POST -t \"Memo Title\" -b \"Memo body here.\""
  echo "  ${0} -X PATCH -t \"Patched title.\" -i 7"
  echo "  ${0} -X PATCH -b \"Patched body.\" -i 7"
  echo "  ${0} -X PUT -t \"New Title\" -b \"New body.\" -i 7"
  echo "  ${0} -X DELETE -i 7"
  exit ${1}

while getopts "o:s:r:X:H:i:t:b:h" opt
  case "${opt}" in
    o) HOST="${OPTARG}" ;;
    s) SCOPE="${OPTARG}" ;;
    r) ROUTE="${OPTARG}" ;;
    X) METHOD="${OPTARG}" ;;
    H) HEADERS="${OPTARG}" ;;
    i) ID="${OPTARG}" ;;
    t) TITLE="${OPTARG}" ;;
    b) BODY="${OPTARG}" ;;
    h) usage 1 ;;
    \?) usage 2 ;;
shift $(expr ${OPTIND} - 1)

case "${METHOD}" in
    curl -H "${HEADERS}" -X ${METHOD} "${HOST}/${SCOPE}/${ROUTE}${ID:+"/${ID}"}"
    PAYLOAD='{"memo": {"title": "'"${TITLE:-(no title)}"'", "body": "'"${BODY:-(no body)}"'"}}'
    curl -H "${HEADERS}" -X ${METHOD} -d "${PAYLOAD}" "${HOST}/${SCOPE}/${ROUTE}" 
    PAYLOAD='{"memo": {"title": "'"${TITLE:-(no title)}"'", "body": "'"${BODY:-(no body)}"'"}}'
    curl -H "${HEADERS}" -X ${METHOD} -d "${PAYLOAD}" "${HOST}/${SCOPE}/${ROUTE}/${ID:?'No ID specified.'}" 
    # if defined replace individual fields with
    # JSON fragments followed by a comma and space
    TITLE=${TITLE:+"\"title\": \"${TITLE}\", "}
    BODY=${BODY:+"\"body\": \"${BODY}\", "}
    # strip trailing comma and space
    PAYLOAD="$(echo "${TITLE}${BODY}" | sed 's/, $//g')"
    # complete JSON payload
    PAYLOAD="{\"memo\": {${PAYLOAD}}}"
    curl -H "${HEADERS}" -X ${METHOD} -d "${PAYLOAD}" "${HOST}/${SCOPE}/${ROUTE}/${ID:?'No ID specified.'}" 
    curl -H "${HEADERS}" -X ${METHOD} "${HOST}/${SCOPE}/${ROUTE}/${ID:?'No ID specified.'}"
    usage 2
echo ""

The reset function resets the variables to their initial state. It is called before parsing command line arguments and displaying the usage.

The usage function displays usage, options and examples. It also terminates the script.

The getopts loop parses command line arguments into variables.

The case statement at the end uses the HTTP method to select a curl call.

  • The GET method works with or without an id.
  • The POST method creates a payload and posts it.
  • PUT is like post except the verb is different and it requires an id.
  • PATCH is the most complicated. It builds a payload and strips the trailing comma. Then it sends the payload to a URL with an id.
  • DELETE requires an id.

The script can be used as follows. Note that trying to delete a memo that does not exist will fail with a wall of HTML.

chmod +x memo_api.sh
./memo_api.sh -X POST -t "Memo Title" -b "Memo body here."
./memo_api.sh -X GET -i 1
./memo_api.sh -X POST -t "Another Memo" -b "This memo's body."
./memo_api.sh -X PATCH -t "Patched title." -i 2
./memo_api.sh -X PATCH -b "Patched body." -i 1
./memo_api.sh -X PUT -t "New Title" -b "New body." -i 2
./memo_api.sh -X GET
./memo_api.sh -X DELETE -i 1

This script could be customized to work with other APIs.