Identity

Property	Value
Binary	`curl`, `wget`
Config	`~/.curlrc` (curl), `~/.wgetrc` (wget)
Logs	No persistent logs — output to terminal
Type	CLI tool
Install	`apt install curl wget` / `dnf install curl wget`

Key Operations

Task	Command
GET request	`curl https://example.com/api/v1/items`
Follow redirects	`curl -L https://example.com`
Save output to file	`curl -o output.json https://example.com/data.json`
Save using remote filename	`curl -O https://example.com/file.tar.gz`
POST with form data	`curl -X POST -d 'key=value&other=123' https://example.com/form`
POST JSON body	`curl -X POST -H 'Content-Type: application/json' -d '{"key":"value"}' https://api.example.com/`
Show response headers only	`curl -I https://example.com`
Show headers and body	`curl -v https://example.com`
Silent (no progress bar)	`curl -s https://example.com/api`
Fail on HTTP error (4xx/5xx)	`curl -sf https://example.com/api`
Basic auth	`curl -u username:password https://example.com/api`
Bearer token	`curl -H 'Authorization: Bearer TOKEN' https://api.example.com/`
Skip TLS verification (testing only)	`curl -k https://self-signed.example.com`
Use client certificate	`curl --cert client.crt --key client.key https://api.example.com/`
Resume interrupted download	`curl -C - -O https://example.com/large.tar.gz`
Limit download speed	`curl --limit-rate 500k -O https://example.com/large.tar.gz`
POST file as body	`curl -X POST --data @payload.json -H 'Content-Type: application/json' https://api.example.com/`
wget: simple download	`wget https://example.com/file.tar.gz`
wget: recursive download	`wget -r -np https://example.com/files/`
wget: mirror a site	`wget --mirror --convert-links https://example.com/`

Symptom	Cause	Fix
Script ignores HTTP 404/500 errors	curl exits 0 on HTTP errors unless `--fail` is set	Add `-f` (`--fail`) so curl exits non-zero on 4xx/5xx
`curl: (60) SSL certificate problem`	Self-signed or expired cert	Use `-k` for testing; for production, fix the cert or provide `-cacert ca.crt`
Redirect not followed	Missing `-L` flag	Add `-L` to follow 301/302/307 redirects
`@` in `-d` data causes "file not found"	curl treats `@` in `-d` as a file reference	URL-encode as `%40`, or use `--data-urlencode 'field=user@example.com'`
`--data @file` sends literal `@file` text	Used `--data` instead of `--data-binary` or correct flag	Use `--data @filename` — the `@` prefix means "read from file" (it works as documented)
wget downloads HTML index instead of file	Server returns directory listing for the URL	Append the actual filename to the URL, or use `curl -O`
Rate limit not working	`--limit-rate` uses bytes/s by default (K/M suffixes optional)	Use `--limit-rate 500k` for 500 KB/s or `--limit-rate 5m` for 5 MB/s

curl exits 0 on HTTP errors: By default, curl treats any HTTP response as success. A script that does curl https://api/ && do_thing will call do_thing even on a 503. Add -f or --fail to fix this; combine with -s to suppress progress noise in scripts.
-o vs -O are easy to confuse: -o filename saves to a local name you specify. -O saves using the remote filename from the URL. Using the wrong one either overwrites an unintended file or saves to a confusing name.
-k skips TLS verification silently: There is no warning in the output that certificate validation was skipped. Fine for internal testing; dangerous in production scripts or CI where it may mask certificate problems.
URL-encoding gotchas with -d: -d sends data URL-encoded if you build it as key=value, but if your value contains &, +, or @, they need manual encoding or use --data-urlencode key=value which handles the encoding automatically.
wget is simpler for downloads, weaker for APIs: wget follows redirects by default and handles resumption well, but lacks curl's header/auth/body control. For anything beyond a simple download, prefer curl.