cURL User Guide

cURL is a command-line tool and library for transferring data. It supports various protocols including HTTP, HTTPS, FTP, and more. cURL is particularly useful in web development for performing HTTP requests, file downloads, and API calls. ServBay comes with cURL pre-installed, and this article will provide a detailed introduction to the installation, configuration, and usage of cURL.

Table of Contents

• Table of Contents
• Installation and Configuration
  • Installation
  • Configuration
• Basic Usage
  • Sending an HTTP GET Request
  • Sending an HTTP POST Request
  • Downloading a File
  • Uploading a File
• Advanced Usage
  • Setting HTTP Headers
  • Handling JSON Data
  • Handling Cookies
  • Using a Proxy
  • Limiting Bandwidth
  • Resuming Downloads
  • Verifying SSL Certificate
• Common Issues
  • 1. cURL Command Not Running
  • 2. Errors in Sending Requests
  • 3. File Download or Upload Failure
  • 4. SSL Certificate Verification Failure
• Summary

Installation and Configuration

Installation

ServBay comes with cURL pre-installed, so no additional installation is required.

Configuration

No configuration is required by default.

Basic Usage

cURL offers a wealth of command-line options for various data transfer tasks. Here are some basic usage examples:

Sending an HTTP GET Request

curl -X GET https://api.example.com/data

Sending an HTTP POST Request

curl -X POST -d "param1=value1&param2=value2" https://api.example.com/data

Downloading a File

curl -O https://example.com/file.zip

Uploading a File

curl -X POST -F "file=@/path/to/file" https://api.example.com/upload

Advanced Usage

Setting HTTP Headers

curl -H "Content-Type: application/json" -H "Authorization: Bearer token" https://api.example.com/data

Handling JSON Data

Sending JSON Data

curl -X POST -H "Content-Type: application/json" -d '{"key1":"value1", "key2":"value2"}' https://api.example.com/data

Fetching and Parsing JSON Response (using jq)

curl -s https://api.example.com/data | jq .

Handling Cookies

Saving Cookies to File

curl -c cookies.txt https://example.com

Using Cookies File

curl -b cookies.txt https://example.com

Using a Proxy

curl -x http://proxy.example.com:8080 https://api.example.com/data

Limiting Bandwidth

curl --limit-rate 100K https://example.com/file.zip -O

Resuming Downloads

curl -C - -O https://example.com/largefile.zip

Verifying SSL Certificate

curl --cacert /path/to/ca-bundle.crt https://secure.example.com

Common Issues

1. cURL Command Not Running

• Solution: Check if cURL is correctly installed and ensure the configuration file paths are correct. If the issue persists, review the error logs for more information.

2. Errors in Sending Requests

• Solution: Verify the URL and parameters of the request are correct. Ensure the network connection is stable and that the target server is accessible.

3. File Download or Upload Failure

• Solution: Check that file paths and permissions are correct. Ensure the target server supports the respective file transfer operations.

4. SSL Certificate Verification Failure

• Solution: Ensure the correct CA certificate file is used. The --insecure option can be used to ignore SSL certificate verification (not recommended for production environments).

curl --insecure https://secure.example.com

Summary

cURL is a powerful and flexible command-line tool suitable for various data transfer tasks. This article has introduced how to install, configure, and use cURL in ServBay for HTTP requests, file downloads, and API calls.