cURL to Code: Convert API Requests to Any Language

cURL is the universal tool for testing APIs. Learn to convert cURL commands to production code in any language.

Understanding cURL Syntax

Basic Structure

curl [options] [URL]

# Common options:
# -X, --request    HTTP method (GET, POST, PUT, DELETE)
# -H, --header     Add header
# -d, --data       Request body
# -u, --user       Basic auth
# -k, --insecure   Skip SSL verification
# -v, --verbose    Show details

Example cURL Commands

# GET request with headers
curl -X GET "https://api.example.com/users"   -H "Authorization: Bearer token123"   -H "Accept: application/json"

# POST with JSON body
curl -X POST "https://api.example.com/users"   -H "Content-Type: application/json"   -d '{"name": "John", "email": "john@example.com"}'

# POST with form data
curl -X POST "https://api.example.com/upload"   -F "file=@document.pdf"   -F "name=My Document"

# Basic authentication
curl -u username:password "https://api.example.com/secure"

Converting to PHP

Using cURL Extension

<?php
// Original: curl -X POST "https://api.example.com/users" //   -H "Content-Type: application/json" //   -d '{"name": "John"}'

$ch = curl_init();

curl_setopt_array($ch, [
    CURLOPT_URL => 'https://api.example.com/users',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_HTTPHEADER => [
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => json_encode([
        'name' => 'John'
    ]),
]);

$response = curl_exec($ch);
$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);

echo $response;
?>

Using Guzzle

<?php
use GuzzleHttpClient;

$client = new Client();

$response = $client->post('https://api.example.com/users', [
    'headers' => [
        'Content-Type' => 'application/json',
    ],
    'json' => [
        'name' => 'John'
    ]
]);

echo $response->getBody();
?>

Converting to JavaScript

Using Fetch API

// Original: curl -X POST "https://api.example.com/users" //   -H "Authorization: Bearer token123" //   -H "Content-Type: application/json" //   -d '{"name": "John"}'

const response = await fetch('https://api.example.com/users', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer token123',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    name: 'John'
  })
});

const data = await response.json();
console.log(data);

Using Axios

const axios = require('axios');

const response = await axios.post('https://api.example.com/users', {
  name: 'John'
}, {
  headers: {
    'Authorization': 'Bearer token123',
    'Content-Type': 'application/json'
  }
});

console.log(response.data);

Converting to Python

Using Requests

import requests

# Original: curl -X POST "https://api.example.com/users" #   -H "Content-Type: application/json" #   -d '{"name": "John"}'

response = requests.post(
    'https://api.example.com/users',
    headers={
        'Content-Type': 'application/json',
    },
    json={
        'name': 'John'
    }
)

print(response.json())

File Upload

# Original: curl -F "file=@document.pdf" https://api.example.com/upload

with open('document.pdf', 'rb') as f:
    response = requests.post(
        'https://api.example.com/upload',
        files={'file': f}
    )

Common cURL Options Mapping

cURL Option	PHP	JavaScript	Python
-X POST	CURLOPT_CUSTOMREQUEST	method: 'POST'	method='POST'
-H "Header: Value"	CURLOPT_HTTPHEADER	headers: {}	headers={}
-d "data"	CURLOPT_POSTFIELDS	body:	data=
-u user:pass	CURLOPT_USERPWD	Authorization header	auth=()
-k	CURLOPT_SSL_VERIFYPEER	agent	verify=False

Handling Edge Cases

Form Data

// cURL: curl -X POST -d "name=John&email=john@example.com" URL

const formData = new URLSearchParams();
formData.append('name', 'John');
formData.append('email', 'john@example.com');

fetch(url, {
  method: 'POST',
  body: formData
});

Basic Auth

// cURL: curl -u username:password URL

const credentials = btoa('username:password');
fetch(url, {
  headers: {
    'Authorization': `Basic ${credentials}`
  }
});

Cookies

// cURL: curl -b "session=abc123" URL

fetch(url, {
  credentials: 'include',
  headers: {
    'Cookie': 'session=abc123'
  }
});

Automated Conversion

// Simple cURL parser
function parseCurl(curlCommand) {
  const result = {
    method: 'GET',
    url: '',
    headers: {},
    body: null
  };

  // Extract URL
  const urlMatch = curlCommand.match(/"(https?://[^"]+)"/);
  if (urlMatch) result.url = urlMatch[1];

  // Extract method
  const methodMatch = curlCommand.match(/-Xs+(w+)/);
  if (methodMatch) result.method = methodMatch[1];

  // Extract headers
  const headerMatches = curlCommand.matchAll(/-Hs+"([^:]+):s*([^"]+)"/g);
  for (const match of headerMatches) {
    result.headers[match[1]] = match[2];
  }

  // Extract data
  const dataMatch = curlCommand.match(/-ds+'([^']+)'/);
  if (dataMatch) result.body = dataMatch[1];

  return result;
}

Try Our Tools

• cURL to PHP - Convert cURL to PHP code

Conclusion

Converting cURL commands to code is essential for API development. Understanding the mapping between cURL options and language-specific HTTP clients makes this process straightforward.