curl - HTTP Client

Command-line tool for making HTTP requests and transferring data.

Basic Requests

GET requests

# Simple GET request
curl https://api.example.com
Save output to file
curl https://example.com -o output.html
curl https://example.com/file.zip -O  # Use remote filename
Follow redirects
curl -L https://example.com
Show response headers
curl -i https://example.com
Show only headers
curl -I https://example.com
Verbose output (debugging)

curl -v https://example.com

POST requests

# POST with data
curl -X POST https://api.example.com/users \
  -d "name=John&email=john@example.com"
POST JSON data
curl -X POST https://api.example.com/users 

-H "Content-Type: application/json" 

-d '{"name":"John","email":"john@example.com"}'
POST from file
curl -X POST https://api.example.com/users 

-H "Content-Type: application/json" 

-d @data.json
Form upload

curl -X POST https://api.example.com/upload 

-F "file=@document.pdf" 

-F "description=My document"

Other HTTP methods

# PUT request
curl -X PUT https://api.example.com/users/1 \
  -H "Content-Type: application/json" \
  -d '{"name":"Jane"}'
DELETE request
curl -X DELETE https://api.example.com/users/1
PATCH request

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

-H "Content-Type: application/json" 

-d '{"email":"newemail@example.com"}'

Headers & Authentication

Custom headers

# Add custom header
curl -H "User-Agent: MyApp/1.0" https://example.com
Multiple headers

curl -H "Accept: application/json" 

-H "Authorization: Bearer token123" 

https://api.example.com

Authentication

# Basic auth
curl -u username:password https://api.example.com
Bearer token
curl -H "Authorization: Bearer YOUR_TOKEN" 

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

https://api.example.com
API key in URL

curl "https://api.example.com?api_key=your_key"

Advanced Features

Timeouts & retries

# Connection timeout (seconds)
curl --connect-timeout 10 https://example.com
Max time for entire operation
curl --max-time 30 https://example.com
Retry on failure
curl --retry 3 https://example.com
Retry delay

curl --retry 3 --retry-delay 5 https://example.com

Cookies

# Send cookies
curl -b "session=abc123" https://example.com
Save cookies to file
curl -c cookies.txt https://example.com
Load cookies from file
curl -b cookies.txt https://example.com
Both save and load

curl -b cookies.txt -c cookies.txt https://example.com

Proxy

# Use HTTP proxy
curl -x http://proxy.example.com:8080 https://api.example.com
With proxy authentication
curl -x http://proxy:8080 -U user:pass https://api.example.com
SOCKS proxy

curl --socks5 127.0.0.1:1080 https://api.example.com

SSL/TLS

# Ignore SSL certificate errors (not recommended for production)
curl -k https://self-signed.example.com
Use specific SSL version
curl --tlsv1.2 https://example.com
Use client certificate
curl --cert client.crt --key client.key https://example.com
Show SSL handshake details

curl -v https://example.com 2>&1 | grep -i ssl

Response Handling

Output formatting

# Silent mode (no progress bar)
curl -s https://api.example.com
Show only HTTP status code
curl -s -o /dev/null -w "%{http_code}" https://example.com
Custom output format
curl -w "\nTime: %{time_total}s\nStatus: %{http_code}\n" 

https://example.com
Pretty print JSON (with jq)
curl -s https://api.example.com | jq '.'

Range requests

# Download specific byte range
curl -r 0-1000 https://example.com/large-file.zip
Resume download

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

File Operations

Downloading files

# Download file
curl -O https://example.com/file.zip
Download with custom name
curl -o myfile.zip https://example.com/file.zip
Download multiple files
curl -O https://example.com/file1.zip 

-O https://example.com/file2.zip
Resume interrupted download

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

Uploading files

# FTP upload
curl -T file.txt ftp://ftp.example.com/upload/
HTTP PUT upload
curl -T file.txt https://example.com/upload
Form file upload

curl -F "file=@document.pdf" https://example.com/upload

Testing & Debugging

API testing

# Test REST API
curl -X GET https://api.example.com/users
curl -X GET https://api.example.com/users/1
curl -X POST https://api.example.com/users -d @user.json
curl -X PUT https://api.example.com/users/1 -d @updated.json
curl -X DELETE https://api.example.com/users/1
Test with verbose output

curl -v -X POST https://api.example.com/login 

-H "Content-Type: application/json" 

-d '{"username":"test","password":"pass"}'

Performance testing

# Measure request time
curl -w "Total time: %{time_total}s\n" https://example.com
Detailed timing
curl -w "\nDNS: %{time_namelookup}s\nConnect: %{time_connect}s\nTLS: %{time_appconnect}s\nTransfer: %{time_starttransfer}s\nTotal: %{time_total}s\n" 

-o /dev/null -s https://example.com

Common debugging

# Show request and response headers
curl -v https://api.example.com
Trace request
curl --trace-ascii trace.txt https://api.example.com
Include response headers in output

curl -i https://api.example.com

Common Patterns

Quick JSON API test:

curl -s https://api.github.com/users/octocat | jq '{name, bio, followers}'

Download with progress bar:

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

POST JSON and extract field:

curl -s -X POST https://api.example.com/login \
  -H "Content-Type: application/json" \
  -d '{"user":"test","pass":"secret"}' | jq -r '.token'

Check if URL is accessible:

if curl -s --head --fail https://example.com > /dev/null; then
  echo "Site is up"
else
  echo "Site is down"
fi

Parallel downloads:

for i in {1..10}; do
  curl -O https://example.com/file$i.jpg &
done
wait

Useful Flags

```
-X
```
: HTTP method (GET, POST, PUT, DELETE, etc.)
```
-d
```
: Data to send (POST/PUT)
```
-H
```
: Custom header
```
-o
```
: Output file
```
-O
```
: Save with remote filename
```
-L
```
: Follow redirects
```
-i
```
: Include headers in output
```
-I
```
: Headers only
```
-v
```
: Verbose output
```
-s
```
: Silent mode
```
-S
```
: Show errors even in silent mode
```
-f
```
: Fail silently on HTTP errors
```
-k
```
: Insecure (ignore SSL)
```
-u
```
: Basic authentication
```
-F
```
: Multipart form data
```
-b
```
: Send cookies
```
-c
```
: Save cookies
```
-w
```
: Custom output format

Tips

Use
```
-s
```
in scripts to suppress progress bar
Combine
```
-sS
```
for silent but show errors
Use
```
-L
```
for redirects (e.g., shortened URLs)
Add
```
-v
```
for debugging
Use
```
jq
```
to process JSON responses
Save common requests as shell aliases or scripts
Use
```
--config
```
for complex reusable requests

Documentation

Official docs: https://curl.se/docs/ Manual:

man curl

HTTP methods: https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods

Curl Http

AI Skill Market Insights

Be Part of the 0+ Developer Community

curl - HTTP Client

Basic Requests

GET requests

Save output to file

Follow redirects

Show response headers

Show only headers

Verbose output (debugging)

POST requests

POST JSON data

POST from file

Form upload

Other HTTP methods

DELETE request

PATCH request

Headers & Authentication

Custom headers

Multiple headers

Authentication

Bearer token

API key in header

API key in URL

Advanced Features

Timeouts & retries

Max time for entire operation

Retry on failure

Retry delay

Cookies

Save cookies to file

Load cookies from file

Both save and load

Proxy

With proxy authentication

SOCKS proxy

SSL/TLS

Use specific SSL version

Use client certificate

Show SSL handshake details

Response Handling

Output formatting

Show only HTTP status code

Custom output format

Pretty print JSON (with jq)

Range requests

Resume download

File Operations

Downloading files

Download with custom name

Download multiple files

Resume interrupted download

Uploading files

HTTP PUT upload

Form file upload

Testing & Debugging

API testing

Test with verbose output

Performance testing

Detailed timing

Common debugging

Trace request

Include response headers in output

Common Patterns

Useful Flags

Tips

Documentation

Quick Start

Manual Installation

TEAR & SHARE

Tags

Channels

Learn

Compare

Company