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cURL Cheatsheet

Command-line tool for transferring data with URLs.

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## cURL Cheatsheet

## 🧰 Installation

# Install curl (Linux/Debian-based)
sudo apt-get install curl

# Install curl (Linux/RPM-based)
sudo yum install curl

# Install curl (macOS with Homebrew)
brew install curl

# Verify installation
curl --version

## 🔰 Basic Usage

Command Description
curl <url> Basic GET request
curl -o output.html <url> Download and save to a file
curl -O <url> Download and save with remote filename
curl -L <url> Follow redirects
curl -i <url> Show headers and response
curl -I <url> Show only HTTP headers
curl -s <url> Silent mode (no progress or errors)
curl -v <url> Verbose/debug output

## 🔐 Authentication & Headers

Command Description
curl -u user:pass <url> Basic auth
curl -H "Authorization: Bearer <token>" <url> Bearer token auth
curl -H "Content-Type: application/json" <url> Set Content-Type header
curl -A "Mozilla/5.0" <url> Set User-Agent header
curl -b "name=value" <url> Send cookie
curl -c cookies.txt <url> Save cookies to file
curl -b cookies.txt <url> Use saved cookies
Chain multiple -H flags to send multiple headers E.g., curl -H "X-API-Key: key" -H "Accept: application/json"

## 📤 Sending Data & HTTP Methods

Command Description
curl -X POST -d "key=value" <url> POST form data
curl -X POST -d @data.json -H "Content-Type: application/json" <url> POST JSON payload
curl -X PUT -d '{"key":"value"}' <url> PUT request with JSON
curl -X PATCH -d '{"key":"newvalue"}' <url> PATCH request
curl -X DELETE <url> DELETE request
curl --data-urlencode "param=value with spaces" <url> URL-encoded POST data

## 📁 File Uploads & Transfers

Command Description
curl -F "file=@/path/to/file.txt" <url> Upload a file via POST
curl -F "file1=@file1.txt" -F "file2=@file2.txt" <url> Upload multiple files
curl -T file.txt ftp://ftp.example.com --user user:pass Upload file via FTP
curl -O <url1> -O <url2> Download multiple URLs
curl -C - -O <url> Resume interrupted download

## ⚙️ Advanced Features

Command Description
curl --proxy http://proxy.example.com:8080 <url> Use a proxy
curl -k <url> Ignore SSL verification (insecure)
curl --max-time 10 <url> Set max timeout in seconds
curl --limit-rate 100K <url> Limit download speed
curl --compressed <url> Request compressed response
curl --http2 <url> Use HTTP/2 protocol

## 🔍 Debugging & Output Handling

Command Description
curl --trace-ascii trace.txt <url> Trace full request/response
curl -v <url> Verbose request and response info
curl <url> > output.html Save output to a file
curl <url> | grep "text" Pipe output to another command
curl <url> | jq . Pretty-print JSON (with jq installed)

## 🧪 Examples

# Download a webpage and save it
curl -o webpage.html https://example.com

# POST JSON data to API
curl -X POST -H "Content-Type: application/json" -d '{"name":"test"}' http://api.example.com

# Authenticate and download with progress bar
curl -u user:pass --progress-bar -O https://example.com/secure/file.zip

# Test API with custom headers
curl -H "Authorization: Bearer abc123" -H "Accept: application/json" https://api.example.com/v1/data

## 💡 Tips

  • Combine -s (silent) with -o or -O to suppress progress but save output.
  • Use -k only for testing; it bypasses SSL verification and is insecure.
  • Chain multiple -H flags to send multiple headers.
  • Use --data-urlencode for URL-encoded POST data.
  • Check man curl or curl --help for full option list.

## 🔗 Resources

Note: Replace URLs, filenames, tokens, and credentials with your actual values. Avoid exposing sensitive data in command history or logs.