curl and wget: HTTP Debugging and API Testing from CLI

curl Basics

# GET request
curl https://api.example.com/users

# Verbose output (headers + body)
curl -v https://api.example.com/users

# Show only response headers
curl -I https://api.example.com/users

# Custom headers
curl -H "Authorization: Bearer TOKEN"      -H "Content-Type: application/json"      https://api.example.com/protected

REST API Operations

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

# PUT
curl -X PUT https://api.example.com/users/1   -H "Content-Type: application/json"   -d '{"name": "Alice Updated"}'

# DELETE
curl -X DELETE https://api.example.com/users/1

# File upload (multipart)
curl -X POST https://api.example.com/upload   -F "file=@/path/to/file.pdf"   -F "name=document"

Authentication

# Basic auth
curl -u username:password https://api.example.com

# Bearer token
curl -H "Authorization: Bearer eyJhbGci..." https://api.example.com

# API key
curl "https://api.example.com/data?api_key=YOUR_KEY"

Response Handling

# Save response to file
curl -o output.json https://api.example.com/data

# Follow redirects
curl -L https://example.com

# Show status code
curl -o /dev/null -w "%{http_code}" https://api.example.com/health

# Pretty print JSON (with jq)
curl https://api.example.com/users | jq '.[] | {id, name}'

wget for Downloads

# Download file
wget https://example.com/file.zip

# Download with custom filename
wget -O myfile.zip https://example.com/file.zip

# Recursive download
wget -r -l2 https://example.com/docs/

# Resume interrupted download
wget -c https://example.com/largefile.iso

Debugging Tips

# Timing breakdown
curl -o /dev/null -w "
Connect: %{time_connect}s
TTFB: %{time_starttransfer}s
Total: %{time_total}s
" https://api.example.com

# SSL certificate info
curl -v --ssl-no-revoke https://example.com 2>&1 | grep -A5 "Server certificate"

# Proxy debugging
curl -x http://proxy:8080 https://api.example.com

curl is the Swiss Army knife of HTTP debugging for developers.