curl Tips and Tricks for API Work

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# GET (default)
curl https://api.example.com/users

# POST with data
curl -X POST https://api.example.com/users \
  -d '{"name":"Alice"}'

# Other methods
curl -X PUT ...
curl -X DELETE ...
curl -X PATCH ...

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# Set content type
curl -H "Content-Type: application/json" ...

# Auth header
curl -H "Authorization: Bearer TOKEN" ...

# Multiple headers
curl -H "Content-Type: application/json" \
     -H "Authorization: Bearer TOKEN" \
     -H "X-Custom-Header: value" ...

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

# From file
curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d @data.json

# Pretty output (pipe to jq)
curl -s https://api.example.com/users | jq

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

# Only headers (no body)
curl -I https://api.example.com/users

# HTTP status code only
curl -s -o /dev/null -w "%{http_code}" https://api.example.com/users

# Timing info
curl -w "Time: %{time_total}s\n" -o /dev/null -s https://api.example.com

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

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

# API key in header
curl -H "X-API-Key: abc123" https://api.example.com

# API key in query
curl "https://api.example.com?api_key=abc123"

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# URL-encoded form
curl -X POST https://example.com/login \
  -d "username=alice&password=secret"

# Multipart form (file upload)
curl -X POST https://example.com/upload \
  -F "file=@photo.jpg" \
  -F "description=My photo"

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# Follow redirects (3xx)
curl -L https://example.com/redirect

# Show redirect chain
curl -L -v https://example.com/redirect 2>&1 | grep "< HTTP\|< Location"

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# Ignore SSL errors (dev only!)
curl -k https://self-signed.example.com

# Use specific cert
curl --cacert /path/to/ca.crt https://api.example.com

# Client cert authentication
curl --cert client.crt --key client.key https://api.example.com

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# Connection timeout (seconds)
curl --connect-timeout 5 https://api.example.com

# Max time for entire operation
curl --max-time 30 https://api.example.com

# Both
curl --connect-timeout 5 --max-time 30 https://api.example.com

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# Verbose output
curl -v https://api.example.com

# Even more verbose (includes SSL handshake)
curl -vv https://api.example.com

# Trace everything to file
curl --trace trace.log https://api.example.com

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

# Save with remote filename
curl -O https://example.com/file.zip

# Silent mode (no progress)
curl -s https://api.example.com

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# Send cookie
curl -b "session=abc123" https://example.com

# Save cookies to file
curl -c cookies.txt https://example.com/login -d "user=alice"

# Send cookies from file
curl -b cookies.txt https://example.com/dashboard

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# Retry on failure
curl --retry 3 https://api.example.com

# Retry with delay
curl --retry 3 --retry-delay 2 https://api.example.com

# Retry on specific errors
curl --retry 3 --retry-connrefused https://api.example.com

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# JSON POST
alias curlj='curl -H "Content-Type: application/json"'

# Pretty JSON output
alias curljq='curl -s | jq'

# Show just status code
alias curlstatus='curl -s -o /dev/null -w "%{http_code}\n"'

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curl -s -X GET "https://api.example.com/users/123" \
  -H "Authorization: Bearer $TOKEN" | jq

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curl -s -X POST "https://api.example.com/users" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"name":"Alice","email":"alice@example.com"}' | jq

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curl -X POST "https://api.example.com/upload" \
  -H "Authorization: Bearer $TOKEN" \
  -F "file=@report.pdf" \
  -F "folder=documents"

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#!/bin/bash
STATUS=$(curl -s -o /dev/null -w "%{http_code}" https://api.example.com/health)
if [ "$STATUS" != "200" ]; then
    echo "API is down! Status: $STATUS"
    exit 1
fi

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curl -s -o /dev/null -w "
DNS:        %{time_namelookup}s
Connect:    %{time_connect}s
TLS:        %{time_appconnect}s
Start:      %{time_starttransfer}s
Total:      %{time_total}s
" https://api.example.com

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