const units = await client.units.retrieve([{ externalId: 'temperature:deg_c' }, { externalId: 'pressure:bar' }]);

res = client.units.retrieve('temperature:deg_c')

res = client.units.retrieve(['temperature:deg_c', 'pressure:bar'])

curl --request POST \
  --url https://{cluster}.cognitedata.com/api/v1/projects/{project}/units/byids \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "items": [
    {
      "externalId": "<string>"
    }
  ],
  "ignoreUnknownIds": false
}
'

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://{cluster}.cognitedata.com/api/v1/projects/{project}/units/byids",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'items' => [
        [
                'externalId' => '<string>'
        ]
    ],
    'ignoreUnknownIds' => false
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://{cluster}.cognitedata.com/api/v1/projects/{project}/units/byids"

	payload := strings.NewReader("{\n  \"items\": [\n    {\n      \"externalId\": \"<string>\"\n    }\n  ],\n  \"ignoreUnknownIds\": false\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://{cluster}.cognitedata.com/api/v1/projects/{project}/units/byids")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"items\": [\n    {\n      \"externalId\": \"<string>\"\n    }\n  ],\n  \"ignoreUnknownIds\": false\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://{cluster}.cognitedata.com/api/v1/projects/{project}/units/byids")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"items\": [\n    {\n      \"externalId\": \"<string>\"\n    }\n  ],\n  \"ignoreUnknownIds\": false\n}"

response = http.request(request)
puts response.read_body

{
  "items": [
    {
      "externalId": "temperature:deg_c",
      "name": "DEG_C",
      "longName": "degree Celsius",
      "symbol": "°C",
      "aliasNames": [
        "°C",
        "C",
        "deg C",
        "degC",
        "DegC"
      ],
      "quantity": "Temperature",
      "conversion": {
        "multiplier": 1,
        "offset": 273.15
      },
      "source": "qudt.org",
      "sourceReference": "http://qudt.org/vocab/unit/DEG_C"
    }
  ]
}

{
  "message": "<string>",
  "code": 123
}