curl

Make an HTTP GET request and dump the contents in stdout

$ curl [https://example.com]

$ curl [[-L|--location]] [[-D|--dump-header]] - [https://example.com]

$ curl [[-O|--remote-name]] [https://example.com/filename.zip]

$ curl [[-X|--request]] POST [[-d|--data]] ['name=bob'] [http://example.com/form]

$ curl [[-k|--insecure]] [[-x|--proxy]] [http://127.0.0.1:8080] [[-H|--header]] ['Authorization: Bearer token'] [[-X|--request]] [GET|PUT|POST|DELETE|PATCH|...] [https://example.com]

$ curl [[-d|--data]] ['{"name":"bob"}'] [[-H|--header]] ['Content-Type: application/json'] [http://example.com/users/1234]

$ curl [[-E|--cert]] [client.pem] --key [key.pem] [[-k|--insecure]] [https://example.com]

$ curl [[-v|--verbose]] --resolve [example.com]:[80]:[127.0.0.1] [http://example.com]

curl [options] [URL...]

Examples:
curl https://example.com
curl -O https://example.com/file.zip
curl -X POST -d "key=value" https://api.example.com/data

-o <file>, --output <file>
    Writes output to <file> instead of standard output.

-O, --remote-name
    Writes output to a file named as the remote file (e.g., if downloading from http://example.com/doc.pdf, saves as doc.pdf).

-L, --location
    Follows HTTP 3xx redirects.

-I, --head
    Fetches only the HTTP header information of a document.

-X <command>, --request <command>
    Specifies a custom request method to use when communicating with the HTTP server (e.g., GET, POST, PUT, DELETE).

-d <data>, --data <data>
    Sends the specified data in a POST request to the HTTP server. Often used for form submissions or sending JSON payloads.

-H <header>, --header <header>
    Passes a custom header to the server (e.g., 'Content-Type: application/json', 'Authorization: Bearer token').

-u <user:password>, --user <user:password>
    Specifies user and password for server authentication.

-k, --insecure
    Allows curl to proceed and operate even if the server's SSL certificate is invalid or cannot be verified. Use with caution.

-s, --silent
    Operates in silent or quiet mode, suppressing the progress meter and error messages.

-v, --verbose
    Makes the operation more talkative, displaying a lot of debugging information.

curl is a robust and widely-used command-line tool for transferring data to or from a server. It supports an extensive array of protocols, including HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, DICT, TELNET, LDAP, LDAPS, FILE, IMAP, POP3, SMTP, and many more.

Developed to work without user interaction, curl is ideal for automated tasks, scripts, and applications. Its capabilities include support for proxies, user authentication, HTTP POST, SSL certificates, cookies, file transfer resume, and Metalink. It's an indispensable tool for developers for testing REST APIs, system administrators for downloading files and managing remote resources, and anyone needing to interact with web services or transfer data over a network.

When using -k or --insecure, curl will bypass SSL certificate verification, which can expose your connection to security risks like Man-in-the-Middle attacks. It should be used only in development or controlled environments.

Be mindful of shell escaping when providing complex URLs or data payloads, especially with special characters or spaces, as the shell might interpret them before curl receives them.

For very large file transfers, consider using -o to stream directly to a file to avoid potential memory issues with very large in-memory buffers.

Beyond being a command-line tool, curl is built upon the highly portable and powerful libcurl library. This library is widely used in countless software applications, devices, and operating systems to handle network communications, making curl's functionality accessible to developers for integration into their own projects.

curl is frequently used for:

• Downloading files from remote servers.
• Interacting with RESTful APIs (e.g., sending JSON data, fetching XML).
• Debugging network requests and responses.
• Testing web server configurations.
• Automating data transfer in scripts and cron jobs.

curl was first released in 1997 by Daniel Stenberg under the name httpget. Its original purpose was to fetch currency exchange rates for an IRC bot. As its capabilities expanded beyond just HTTP GET requests, it was renamed to curl in 1998, a portmanteau of 'Client for URLs'.

The underlying library, libcurl, was subsequently developed, allowing applications to integrate curl's powerful data transfer capabilities. Over the years, curl has grown to support an impressive number of protocols and features, becoming an almost universal tool for network-related tasks across various operating systems.

wget(1), httpie(1), netcat(1), scp(1), sftp(1)