cURL

Not to be confused with Curl, a programming language with a similar name.

For other uses, see Curl (disambiguation).

cURL

Example output from curl -O
Original author(s)	Daniel Stenberg
Initial release	1997
Stable release	7.31.0 (June 22, 2013 (2013-06-22) ) [±]
Development status	Active
Written in	C
Operating system	Cross-platform
Type	FTP client / HTTP client
License	Free Software: MIT/X derivate license
Website	curl.haxx.se

cURL is a computer software project providing a library and command-line tool for transferring data using various protocols. The cURL project produces two products, libcurl and cURL. It was first released in 1997.

libcurl

libcurl is a free client-side URL transfer library, supporting FTP, FTPS, Gopher, HTTP, HTTPS, SCP, SFTP, TFTP, Telnet, DICT, the file URI scheme, LDAP, LDAPS, IMAP, POP3, SMTP and RTSP. The library supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading, Kerberos, HTTP form based upload, proxies, cookies, user-plus-password authentication, file transfer resume, and HTTP proxy tunneling.

The libcurl library is portable. It builds and works identically on several platforms, including Solaris, NetBSD, FreeBSD, OpenBSD, Darwin, HPUX, IRIX, AIX, Tru64, Linux, UnixWare, HURD, Windows, Symbian, AmigaOS, OS/2, BeOS, Mac OS X, Apple iOS, Android, Ultrix, QNX Neutrino, BlackBerry Tablet OS and BlackBerry 10, OpenVMS, RISC OS, Novell NetWare, DOS and more.

The libcurl library is free, thread-safe, IPv6 compatible, and fast. Bindings are available for more than 40 languages, including C/C++, Java, PHP and Python.

The libcurl library can support SSL/TLS through OpenSSL, GnuTLS, NSS, CyaSSL, PolarSSL, axTLS, QSOSSL on IBM i, Secure Transport on OS X and iOS, and SChannel on Windows.

cURL

A command line tool for getting or sending files using URL syntax.

Since cURL uses libcurl, it supports a range of common Internet protocols, currently including HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, LDAP, LDAPS, DICT, TELNET, FILE, IMAP, POP3, SMTP and RTSP (the last four only in versions newer than 7.20.0 or 9 February 2010).

The name of the project is a play on 'Client for URLs', originally with URL spelled in uppercase to make it obvious that it deals with URLs. The fact that it can also be pronounced 'see URL' also helped; it works as an abbreviation for "Client URL Request Library" or the recursive version: "Curl URL Request Library".

Daniel Stenberg started writing cURL in 1997, as a way to transfer files via protocols such as HTTP, FTP, Gopher, and many more, via a command-line interface. Several other people made important and crucial contributions to the project. Distributed under the MIT License, cURL is free software.

Examples of cURL use from command line

Basic use of cURL involves simply typing curl at the command line, followed by the URL of the output to retrieve.

To retrieve the example.com homepage, type:

curl www.example.com

cURL defaults to displaying the output it retrieves to the standard output specified on the system (usually the terminal window). So running the command above would, on most systems, display the www.example.com source-code in the terminal window.

cURL can write the output it retrieves to a file with the -o flag, thus:

curl -o example.html www.example.com

This will store the source code for www.example.com into a file named example.html. While retrieving output, cURL will display a progress-bar showing how much of the output has downloaded. Note however that cURL does not show a progress bar when preparing to display the output in the terminal window, since a progress-bar is likely to interfere with the display of the output.

To download output to a file that has the same name as on the system it originates from, use the -O flag, for example:

curl -O www.example.com/example.html

If the server responds that the file (example.html) is moved to a different location (indicated with a Location: header and a 3XX response code), use the -L flag, for example:

curl -OL www.example.com/example.html

Curl offers many other features such as proxy support, user authentication, FTP upload, HTTP post, SSL connections, cookies, file transfer resume, Metalink, as well as various other features.

See also

• Wget
• Web crawler
• curl-loader - an open-source testing tool based on cURL
• libwww

External links

• cURL website
• curl manual
• Comparison of cURL vs other open source download tools
• Comparison of cURL vs wget