ncurses (new

curses A curse (also called an imprecation, malediction, execration, malison, anathema, or commination) is any expressed wish that some form of adversity or misfortune will befall or attach to one or more persons, a place, or an object. In particular ...

) is a

programming library In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and su ...

providing an

application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

(API) that allows the programmer to write text-based user interfaces (TUI) in a terminal-independent manner. It is a toolkit for developing "

GUI The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...

-like"

application software Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a ...

that runs under a

terminal emulator A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote term ...

. It also optimizes screen changes, in order to reduce the latency experienced when using remote shells. ncurses is a free-software emulation of the System V Release 4.0 (SVr4)

. There are bindings for ncurses in a variety of programming languages, including

Ada Ada may refer to: Places Africa * Ada Foah, a town in Ghana * Ada (Ghana parliament constituency) * Ada, Osun, a town in Nigeria Asia * Ada, Urmia, a village in West Azerbaijan Province, Iran * Ada, Karaman, a village in Karaman Province, T ...

, Python, Gambas,

Ruby A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called ...

, PHP,

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

, and

Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offic ...

History

As the new version, ncurses is a free-software emulation of the System V Release 4.0 (SVr4)

, which was itself an enhancement over the discontinued 4.4 BSD curses. The XSI Curses standard issued by X/Open is explicitly and closely modeled on

System V Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, an ...

curses

The first curses library was developed at the University of California at Berkeley, for a BSD operating system, around 1980 to support

Rogue A rogue is a person or entity that flouts accepted norms of behavior. Rogue or rogues may also refer to: Companies * Rogue Ales, a microbrewery in Newport, Oregon * Rogue Arts, a film production company * Rogue Entertainment, a software co ...

, a text-based adventure game. It originally used the

termcap Termcap (''terminal capability'') is a software library and database used on Unix-like computers. It enables programs to use display computer terminals in a device-independent manner, which greatly simplifies the process of writing portable text ...

library, which was used in other programs, such as the vi editor. The success of the BSD curses library prompted

Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mul ...

to release an enhanced curses library in their System V Release 2

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, ...

systems. This library was more powerful and instead of using termcap, it used terminfo. However, due to

AT&T AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile ...

policy regarding source-code distribution, this improved curses library did not have much acceptance in the BSD community.

pcurses

Around 1982, Pavel Curtis started work on a

freeware Freeware is software, most often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines ''freeware'' unambiguously; every publisher defines its own rules for the ...

clone of the Bell Labs curses, named pcurses, which was maintained by various people through 1986.

ncurses

The pcurses library was further improved when Zeyd Ben-Halim took over the development effort in late 1991. The new library was released as ncurses in November 1993, with version 1.8.1 as the first major release. Subsequent work, through version 1.8.8 (M1995), was driven by

Eric S. Raymond Eric Steven Raymond (born December 4, 1957), often referred to as ESR, is an American software developer, open-source software advocate, and author of the 1997 essay and 1999 book ''The Cathedral and the Bazaar''. He wrote a guidebook for the ...

, who added the form and menu libraries written by Juergen Pfeifer. Since 1996, it has been maintained by Thomas E. Dickey. Most ncurses calls can be easily ported to the old curses. System V curses implementations can support BSD curses programs with just a recompilation. However, a few areas are problematic, such as handling terminal resizing, since no counterpart exists in the old curses.

Terminal database

Ncurses can use either terminfo (with extensible data) or

. Other implementations of

generally use terminfo; a minority use

. Few (mytinfo was an older exception) use both.

License

Ncurses is a part of the

GNU Project The GNU Project () is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and computing devices by collabor ...

, but is not distributed under the

GNU GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general u ...

LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...

. Instead, it is distributed under a permissive free software licence, i.e., the

MIT License The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts only very limited restriction on reuse and has, therefore, high license comp ...

. This is due to the agreement made with the

Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed under copyleft ( ...

at the time the developers assigned their copyright. When the agreement was made to pass on the rights to the FSF, there was a clause that stated:

The Foundation promises that all distribution of the Package, or of any work "based on the Package", that takes place under the control of the Foundation or its agents or assignees, shall be on terms that explicitly and perpetually permit anyone possessing a copy of the work to which the terms apply, and possessing accurate notice of these terms, to redistribute copies of the work to anyone on the same terms.

According to the maintainer Thomas E. Dickey, this precludes relicensing to the GPL in any version, since it would place restrictions on the programs that will be able to link to the libraries.

Programs using ncurses

There are hundreds of programs which use ncurses. Some, such as

GNU Screen GNU Screen is a terminal multiplexer, a software application that can be used to multiplex several virtual consoles, allowing a user to access multiple separate login sessions inside a single terminal window, or detach and reattach sessions fro ...

and w3m, use only the

interface and perform screen management themselves. Others, such as GNU Midnight Commander and

YaST YaST (Yet another Setup Tool) is a Linux operating system setup and configuration tool. YaST is featured in the openSUSE Linux distribution, as well as in SUSE's derived commercial distributions. It is also part of the defunct United Linux. YaS ...

, use the curses programming interface.

Notes

References

External links

* {{Official website C (programming language) libraries Free software programmed in Ada Free software programmed in C GNU Project software Software using the MIT license Termcap Terminfo