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 t ...

(API) that allows the programmer to write

text-based user interface In computing, text-based user interfaces (TUI) (alternately terminal user interfaces, to reflect a dependence upon the properties of computer terminals and not just text), is a retronym describing a type of user interface (UI) common as an ear ...

s (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 c ...

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 termin ...

. It also optimizes screen changes, in order to reduce the latency experienced when using remote shells. ncurses is a

free-software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...

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, ...

Python Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...

Gambas Gambas is the name of an object-oriented dialect of the BASIC programming language, as well as the integrated development environment that accompanies it. Designed to run on Linux and other Unix-like computer operating systems, its name is a re ...

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 sa ...

PHP PHP is a general-purpose scripting language geared toward web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by The PHP Group ...

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 Website, websites use JavaScript on the Client (computing), client side ...

, 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 offici ...

History

As the new version, ncurses is a

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 X/Open group (also known as the Open Group for Unix Systems and incorporated in 1987 as X/Open Company, Ltd.) was a consortium founded by several European UNIX systems manufacturers in 1984 to identify and promote open standards in the field of info ...

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 The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...

operating system, around 1980 to support Rogue, 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 mult ...

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, and ot ...

systems. This library was more powerful and instead of using termcap, it used

terminfo Terminfo is a library and database that enables programs to use display terminals in a device-independent manner. Mary Ann Horton implemented the first terminfo library in 1981–1982 as an improvement over termcap. The improvements include * fast ...

. 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 tel ...

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

pcurses

Around 1982,

Pavel Curtis Pavel Curtis is an American software architect at Microsoft who is best known for having founded and managed ''LambdaMOO'', an online community. In the mid- to late 1980s Curtis developed and taught parts of the computer science course at the ...

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 f ...

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 A binary recompiler is a compiler that takes executable binary files as input, analyzes their structure, applies transformations and optimizations, and outputs new optimized executable binaries. The foundation to the concepts of binary recompila ...

. 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

(with extensible data) or

. Other implementations of

generally use

; 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 collaborati ...

, 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 us ...

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 A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, ...

, 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)#501(c)(3), 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 ...

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 w3m is a free software/ open source text-based web browser and terminal pager. It has support for tables, frames, SSL connections, color, and inline images on suitable terminals. Generally, it renders pages in a form as true to their origi ...

, use only the

interface and perform screen management themselves. Others, such as

GNU Midnight Commander GNU Midnight Commander (also known as mc, the command used to start it, and as mouseless commander in older versions) is a free cross-platform orthodox file manager. It was started by Miguel de Icaza in 1994 as a clone of the then-popular Nort ...

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