Linux curl Command Explained

curl speaks HTTP, HTTPS, and many other protocols. Set methods with -X, headers with -H, and data with -d. For TLS, --cacert pins trust stores and -k skips verification only for controlled tests. -w prints timing variables after transfer—useful for latency splits. Save bodies with -o and show headers with -D or -i.

Goal	Flags	Note
Follow redirects	`-L`	Combine with max-redirs for safety
JSON POST	`-H Content-Type: application/json` `-d @file`	Use @ to load body from disk
Pin host to IP	`--resolve`	Test vhosts without DNS

What curl does, curl vs wget, DNS troubleshooting, Linux networking commands

Use -i to include headers in stdout or -D file to write headers separately from the body.

After the transfer, -w outputs format variables such as time_namelookup and time_total for performance debugging.

Add Authorization with -H "Authorization: Bearer …" or use --oauth2-bearer when using OAuth2 client flows.

Hostname mismatch, expired certs, or missing intermediates—inspect with -v and fix trust store or chain files.

Use --range for partial content or --max-filesize to abort when responses exceed a threshold.

-d sends application/x-www-form-urlencoded or raw data; -F builds multipart form uploads for files.

Save with -c and load with -b to mimic browser sessions during API debugging.

Modern builds negotiate HTTP/2 over HTTPS when offered; use --http2 or --http1.1 to force a version for tests.

Goal	Flags	Note
Follow redirects	`-L`	Combine with max-redirs for safety
JSON POST	`-H Content-Type: application/json` `-d @file`	Use @ to load body from disk
Pin host to IP	`--resolve`	Test vhosts without DNS