CURL

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cURL [kurl] is the name of the computer software project. The cURL project produces two products libcurl and cURL

libcurl

A free and easy-to-use client-side URL transfer library, supporting FTP, FTPS, HTTP, HTTPS, SCP, SFTP, TFTP, TELNET, DICT, FILE, LDAP and LDAPS. libcurl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading, kerberos, HTTP form based upload, proxies, cookies, user+password authentication, file transfer resume, http proxy tunneling and more.

libcurl is portable, it builds and works identically on several platforms, including Solaris, NetBSD, FreeBSD, OpenBSD, Darwin, HPUX, IRIX, AIX, Tru64, Linux, UnixWare, HURD, Windows, Amiga, OS/2, BeOs, Mac OS X, Ultrix, QNX, OpenVMS, RISC OS, Novell NetWare, DOS and more...

libcurl is free, thread-safe, IPv6 compatible, feature rich, supported and fast. Software programmers may incorporate libcurl into their programs. Bindings in more than 40 languages are available for libcurl.

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 and FILE.

The name of the project is a play on 'Client for URLs', originally with URL spelled in uppercase to make it obvious it deals with URLs. The fact 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 persons 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 might 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:

curl -O (URL)

Supported protocols

Additional format support includes (among many other features):

• HTTPS certificates
• HTTP POST
• HTTP PUT
• FTP uploading
• Kerberos
• HTTP form based upload
• proxies
• cookies
• user+password authentication (Basic, Digest, NTLM, Negotiate for HTTP, and Kerberos 4 for FTP)
• File transfer resume
• HTTP proxy tunneling

Authors and copyright

Daniel Stenberg wrote cURL, with contributions from more than 600 named helpers; notable contributors include Dan Fandrich and Yang Tse. A THANKS file in the distribution names all contributors, great and small.

The copyright of cURL belongs to Daniel Stenberg.

See also

Free software portal

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

References

1. ^ Daniel Stenberg (2009-11-04). "ANNOUNCE: curl and libcurl 7.19.7". curl-announce mailing list. http://article.gmane.org/gmane.comp.web.curl.general/10828. 

External links

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