curl Cheatsheet

Power user.

Overview

curl is the universal HTTP client for command-line work, present on every Unix box and most container images. Five primitives carry most operational use: method support across the full HTTP verb set, header control, body shaping by content type, TLS debugging, and output control for scripting. Fluency turns "is the API up?" into a one-liner instead of a Postman session.

• Method support. GET, POST, PUT, PATCH, DELETE via -X. Full-API access from the shell.
• Headers. -H sets request headers. Supports auth (Bearer, Basic), content-type, custom headers.
• Body data. -d form data, --data-raw arbitrary, -F multipart. Match the content type, not the other way around.
• TLS debug plus output control. -v shows the TLS handshake; --cacert specifies CA bundle; -o, -s, -w shape output for scripting.

The approach

Verbose first when debugging, silent with format string when scripting. Five idioms cover most operational curl use; memorising them turns API troubleshooting into a 30-second exercise.

• curl -v. Verbose mode shows headers, TLS handshake, redirects. First move on every debug session.
• curl -s -w "%{http_code}\n". Silent mode with status code output. Scriptable health checks.
• curl -H "Authorization: Bearer $TOKEN". Header-based auth. Replaces deprecated -u for API tokens.
• JSON POST plus follow redirects. curl --data-raw '{"key":"value"}' -H "Content-Type: application/json"; add -L to follow redirects like a browser.

Why this compounds

Each curl one-liner that lands in muscle memory shortens the next API debug. Reusable scripts turn smoke tests, health checks, and deploy verification into command-line operations the team owns. By year two, curl is the first tool reached for any HTTP question and Postman becomes the optional GUI it always should have been.

• Faster API debugging. One-liners replace GUI clicks. Investigation latency drops.
• Reusable scripts. Health checks, smoke tests, deploy verification. Operations scale without new tooling.
• TLS expertise. curl -v teaches the TLS handshake one investigation at a time. Network knowledge grows.
• Year-one investment, year-two habit. First year builds fluency; by year two, curl is the reflexive first tool for HTTP investigations.