curl

curl is a command-line tool and library for transferring data with URLs. It uses libcurl, a portable, open-source library that provides a consistent API for multiple protocols. Curl supports a wide range of protocols, including HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, DICT, TELNET, LDAP, and more. It is cross-platform and runs on most Unix-like systems, Windows, and macOS.

Curl was created by Daniel Stenberg in 1997 to fetch currency exchange rates. It started as a tool named httpget, later renamed curl, with the libcurl library released shortly afterward to support embedding in other programs.

The tool offers features such as resuming interrupted downloads, cookie handling, user authentication, proxy support, TLS/SSL encryption, compression, and multipart form data.

The command line typically takes a URL as input and outputs the response body. Common options include -O to save to a file, -I to fetch headers, -d to post data, -u for authentication, and -L to follow redirects.

Libcurl is distributed under a permissive license that enables use in open-source and commercial software. The library provides a C API and bindings for many programming languages, making curl widely reused in other applications.