# Announcing ncurses 6.5

## Overview

The ncurses (new curses) library is a free software emulation of curses in System V Release 4.0 (SVr4), and more. It uses terminfo format, supports pads and color and multiple highlights and forms characters and function-key mapping, and has all the other SVr4-curses enhancements over BSD curses. SVr4 curses became the basis of X/Open Curses.

In mid-June 1995, the maintainer of 4.4BSD curses declared that he considered 4.4BSD curses obsolete, and encouraged the keepers of unix releases such as BSD/OS, FreeBSD and NetBSD to switch over to ncurses.

Since 1995, ncurses has been ported to many systems:

- It is used in almost every system based on the Linux kernel (aside from some embedded applications).
- It is used as the system curses library on OpenBSD, FreeBSD and MacOS.
- It is used in environments such as Cygwin and MinGW. The first of these was EMX on OS/2 Warp.
- It is used (though usually not as the system curses) on all of the vendor unix systems, e.g., AIX, HP-UX, IRIX64, SCO, Solaris, Tru64.
- It should work readily on any ANSI/POSIX-conforming unix.

The distribution includes the library and support utilities, including

- captoinfo, a termcap conversion tool
- clear, utility for clearing the screen
- infocmp, the terminfo decompiler
- tabs, set tabs on a terminal
- tic, the terminfo compiler
- toe, list (table of) terminfo entries
- tput, utility for retrieving terminal capabilities in shell scripts
- tset, to initialize the terminal

Full manual pages are provided for the library and tools.

The ncurses distribution is available at ncurses' homepage:

> https://invisible-island.net/archives/ncurses/ or
> https://invisible-mirror.net/archives/ncurses/ .

It is also available at the GNU distribution site

> https://ftp.gnu.org/gnu/ncurses/ .

## Release Notes

These notes are for ncurses 6.5, released April 27, 2024.

This release is designed to be source-compatible with ncurses 5.0 through 6.4; providing extensions to the application binary interface (ABI). Although the source can still be configured to support the ncurses 5 ABI, the reason for the release is to reflect improvements to the ncurses 6 ABI and the supporting utility programs.

There are, of course, numerous other improvements, listed in this announcement.

The most important bug-fixes/improvements dealt with robustness issues. The release notes also mention some other bug-fixes, but are focused on new features and improvements to existing features since ncurses 6.4 release.

### Library improvements

#### New features

These are new features:

- The low-level terminfo and termcap interfaces are used both by the higher-level curses library, as well as by many applications.

  The functions which convert parameterized terminal capability strings for output to the terminal (`tiparm` and `tparm`) analyze the capability string to determine which parameters are strings (i.e., addresses), versus numbers (not addresses).

  The library's analysis of a capability string may differ from the calling application's design if environment variables are used to point to an invalid terminal database. This is a longstanding problem with all implementations of terminfo, dating from the early 1980s.

  Two new functions address this problem: by providing a function which allows the calling application to tell ncurses how many string-parameters to expect:

  - `tiscan_s` helps applications check formatting capabilities that would be passed to `tiparm_s`.
  - `tiparm_s` provides applications a way to tell ncurses what the expected parameters are for a capability.

- The ncurses library supports a compile-time feature (enabled with the configure `--enable-check-size` option) which simplifies initialization with terminals which do not negotiate window (screen) size. This is done in `setupterm`, by providing for using ANSI cursor-position report (in user6/user7 terminfo capabilities) to obtain the screen size if neither environment variables or ioctl is used.

  The ncurses test-program with options “`-E -T`” demonstrates this feature.

- add functions to query tty-flags in `SCREEN`

This release drops compatibility with obsolete versions of tack, e.g., pre-1.08

#### Other improvements

These are improvements to existing features:

- In addition to the new, safer function `tiparm_s`, ncurses adds checks to make the older `tiparm`, `tparm` and `tgoto` functions safer:

  - the terminfo functions `tiparm` and `tparm` ensure that the capability string comes from the terminal description which ncurses loads, rather than from random data which the application happens to have.

  - the `tgoto` function disallows capabilities which its analysis shows will attempt to use string parameters.

  - ncurses uses internal functions which correspond to `tiparm`, and `tgoto` which ensure that the capability strings which are passed to these functions come from the loaded terminal description.

- improve check in `lib_tparm.c`, ensuring that a char* fits into a `TPARM_ARG`

- modify `_nc_syserr_abort` to use `_nc_env_access`, rather than only checking root uid

- improve thread lock in `lib_trace.c`

- modify `flushinp` to use file descriptors in `SCREEN`, rather than from `TERMINAL`, and check if they are for a terminal, like SVr4

- modify `mcprint` to use file descriptor in `SCREEN`, for consistency

- modify internal function `_nc_read_file_entry` to show relevant filename in warnings

- improve checks in internal function `convert_string` for corrupt terminfo entry

- review/improve handling of out-of-memory conditions

- limit delays to 30 seconds, i.e., padding delays in terminfo, as well as `napms` and `delay_output` functions

- fix reallocation loop for `vsnprintf` in `_nc_sprintf_string` by copying the va_list variable

- modify `delscreen` to limit the windows which it creates to just those associated with the screen

- modify `endwin` to return an error if it is called again without an intervening screen update

- modify `wenclose` to handle pads

- eliminate use of `PATH_MAX` in `lib_trace.c`

- provide for any `CCHARW_MAX` greater than 1

These are corrections to existing features:

- correct loop termination condition in `waddnstr` and `waddnwstr`

- improve parsing in internal function `_nc_msec_cost`, allowing a single decimal point

- amend parameter check for entire string versus specific length in `winsnstr` and `wins_nwstr` to match Solaris; make similar correction to `wins_nwstr`

- correct internal function `wadd_wch_literal` when adding a non-spacing character to a double-width character

- correct definition of `Charable` macro for non-wide ncurses library .

### Program improvements

Several improvements were made to the utility programs. Some were done to make the `infocmp` option “`-u`” option help refactor the terminal database.

infocmp

  - add limit checks for processing extended capabilities with the “`-u`” option

  - correct initial alignment of extended capabilities, so that the “`-u`” option can be used for more than two terminal types

  - modify “`-u`” option to not report cancels for strings which were already cancelled in a use'd chunk.

  - correct an assignment “`-u`” for detecting if a boolean is unset in a base entry and set in a use'd chunk, i.e., if it was cancelled.

tic

  - correct limit-check when dumping tc/use clause via “`-I`”

  - check return value of `_nc_save_str`, in special case where extended capabilities are processed but the terminal description was not initialized

  - modify check for multiply defined aliases to report problems within the current runtime rather than for conflicts with pre-existing terminal descriptions.

  - disallow using `$TERMINFO` or `$HOME/.terminfo` when “`-o`” option is used

tput and tset

  - add “`-v`” option to tput, to show warnings

  - modify reset command to avoid altering clocal if the terminal uses a modem

  - modify reset feature to avoid 1-second sleep if running in a pseudo-terminal

#### Examples

Along with the library and utilities, improvements were made to the ncurses-examples:

- modify `test_tparm` to account for extended capabilities

- corrected mouse mask in `test/testcurs.c`

- modify `test/clip_printw.c` to optionally test non-wrapped updates

- modify `test/test_mouse.c` to use curses api for raw/noraw

- modify `test/clip_printw.c` to optionally test non-wrapped updates

There is one new demo/test programs:

test/test_endwin.c

  This program shows the return-status from `endwin` with different combinations of `endwin` (repeated), `initscr`, `newterm`.

### Terminal database

There are several new terminal descriptions:

- `ansi+apparrows`

- `contour`

- `linux+kbs` for terminals which imitate xterm's behavior with Linux

- `rio`, `rio-direct`

- `mostlike`

- `ms-vt100-16color`, `winconsole`

- `vt100+noapp`, `vt100+noapp+pc`, `xterm+app+pc`, `xterm+decedit` from xterm #389

- `putty+cursor` to reflect amending of modified cursor-keys in 2021

- `wezterm`

There are many changes to existing terminal descriptions. Some were updates to several descriptions, using the `infocmp` “`-u`” option in a script to determine which building-block entries could be used to replace multiple capability settings (and trim redundant information).

Other changes include:

- document XF, kxIN and kxOUT

- add note on `sun` regarding wscons/cmdtool/shelltool

- remove DECCOLM+DECSCLM from `foot`

- add xterm+focus to `foot+base`

- add ecma+strikeout to `putty`

- use CSI 3J in `vte-2017`

- use oldxterm+sm+1006 in `vte-2014`

- modify `xgterm` to work around line-drawing bug

- add xterm focus mode 1004 to `xterm+focus` as fe/fd capabilities, like vim.

- add xterm+focus to `alacritty+common`

- add XR/xr, to work with vim, and use RV/rv to denote DA2 and its response

- add XF flag to `xterm+focus` so that termcap applications can be aware of terminals which may support focus in/out

- use xterm+focus in `xterm-p370` and `tmux`

- remove xterm+sm+1006 from `tmux`

- NetBSD-related fixes for `x68k` and `wsvt25`

### Documentation

As usual, this release

- improves documentation by describing new features,

- attempts to improve the description of features which users have found confusing

- fills in overlooked descriptions of features which were described in the NEWS file but treated sketchily in manual pages.

In addition to providing background information to explain these features and show how they evolved, there are corrections, clarifications, etc.:

- Corrections:

  - add assignment in `CF_MAN_PAGES` to fill in value for `TERMINFO_DIRS` in ncurses, terminfo and tic manpages.

  - clarify interaction of `-R` option versus `-C`, `-I` and `-r` in `infocmp` manpage.

  - correct manpage description of panel_hidden.

  - improve manpage description for addch versus unctrl format used for non-printable characters.

  - improve manpages discussing file descriptors in low-level functions.

  - improve description of search rules for terminal descriptions in terminfo manpage.

  - modify dist.mk to avoid passing developer's comments in manpages into the generated html documentation.

  - modify test-package "ncurses6-doc" to use manpage-aliases, which in turn required a change to the configure script to factor in the extra-suffix option when deriving alias names.

- New/improved history and portability sections:

  - add information about "ttycap", termcap's forerunner, to tset.1

  - document limitations of tparm, and error-returns in curs_terminfo.3x

  - document limitations of tgoto, and error-returns in curs_termcap.3x

- Other improvements:

  - This release has many changes to improve the formatting and style of the manpages.

  - Manpages now use consistent section-naming, page headers and footers (including the modification date for each page).

  - Table layout has been revised.

There are no new manual pages (all of the manual page updates are to existing pages).

### Interesting bug-fixes

The changes to `tparm`, `tgoto` which improve the design of the low-level interfaces are interesting, but are not bug-fixes per se.

### Configuration changes

#### Major changes

These are the major changes (aside from introducing `tiparm_s`):

- use wide-character (ncursesw) by default

- use opaque typedefs by default

However, most of the work on configure scripts was done to reduce warnings within the configure script:

- intrusive warnings from GNU grep regarding fgrep and egrep

- fatal errors in compile-checks, arising from recent “Modern C” efforts by some developers which caused longstanding configure checks to fail.

  After repairing the configure script, none of that activity affected ncurses because stricter warnings are used routinely in development.

Other improvements made to configure checks include

- use string-hacks in alloc_entry.c, alloc_type.c and hardscroll.c, overlooked due to compiler changes in recent OpenBSD releases

- revise progs.priv.h to provide for NC_ISATTY reuse

- configure check for MB_LEN_MAX provides warning as needed

- trim a space after some "-R" options, fixing builds for applications built using clang and ncurses on Solaris

- work around misconfiguration of MacPorts gcc13, which exposes invalid definition of `MB_LEN_MAX` in gcc's fallback copy of `limits.h`

- modified experimental Windows driver works with xterm mouse protocol

#### Configuration options

There are a few new configure options:

`--disable-setuid-environ`

  Compile with environment restriction, so certain environment variables are not available when running via a setuid/setgid application. These are (for example `$TERMINFO`) those that allow the search path for the terminfo or termcap entry to be customized.

  A setuid/setgid application inherits its environment variables from the current user, in contrast to sudo which may limit the environment variables that ncurses uses.

`--enable-check-size`

  Compile-in feature to detect screensize for terminals which do not advertise their screensize, e.g., serial terminals.

`--with-abi-altered=NUM`

  Override the displayed (rather than compiled-in) ABI. Only packagers who have created configurations where the ABI differs from ncurses should be interested in this option.

`--with-strip-program=XXX`

  When stripping executables during install, use the specified program rather than “strip” overriding program chosen by the install program for stripping executables.

These configure options are modified:

`--with-pkg-config-libdir[=DIR]`

  The optional DIR parameter can now be “auto” to automatically use pkg-config's library directory.

  The default is `$(libdir)`.

`--with-xterm-kbs[=XXX]`

  The default is “auto” which tells the configure script to choose BS or DEL according to platform defaults.

### Portability

Many of the portability changes are implemented via the configure script:

- add/use configure check for `clock_gettime`, to supersede `gettimeofday`.

- modify configure script check for pkg-config library directory to take into account an older version 0.15.0 which used PKG_CONFIG_PATH but not PKG_CONFIG_LIBDIR

- allow for MinGW32-/64-bit configurations to use _DEFAULT_SOURCE

- modify CF_XOPEN_SOURCE macro's amend default case to avoid undefining _XOPEN_SOURCE if _POSIX_C_SOURCE is defined

- updated configure script macro CF_XOPEN_SOURCE, for uClibc-ng

- modify version-check for gcc/g++, now works for msys2

- build-fixes related to configure-options and/or platform:

  - fix for `--enable-fvisibility`
  - fix for unusual values of `--with-rel-version`
  - fix for unusual values of `--with-abi-version`
  - fix for `--disable-tcap-names`
  - fix for termcap in `nc_access.h`

- other configure-script improvements:

  - recent msys2 headers work with `_DEFAULT_SOURCE`; amend check
  - use `$ac_includes_default` in most cases where stdlib.h should work
  - use `#error` consistently vs "make an error"
  - add configure macro for `gettimeofday` vs inline check

Here are some of the other portability fixes:

- modify configure scripts/makefiles to omit `KEY_RESIZE` if the corresponding `SIGWINCH` feature is disabled

- increase `MB_CUR_MAX` to 16, matching glibc's `MB_LEN_MAX`

- add BSD `erase2` to characters handled by tset/reset

- use `getauxval` when available, to improve `setuid`/`setgid` checks

- set `dwShareMode` in calls to `CreateConsoleScreenBuffer`

- use `CreateFile` with "`CONIN$`", "`CONOUT$`" rather than `GetStdHandle` to obtain a handle on the actual console, avoiding redirection in the MinGW/Win32 configurations

- modify MinGW driver to return `KEY_BACKSPACE` when an unmodified `VK_BACK` virtual key is entered

- modify MinGW configuration to provide for running in MSYS/MSYS2 shells, assuming ConPTY support

## Features of ncurses

The ncurses package is fully upward-compatible with SVr4 (System V Release 4) curses:

- All of the SVr4 calls have been implemented (and are documented).

- ncurses supports the features of SVr4 curses including keyboard mapping, color, form drawing with ACS characters, and automatic recognition of keypad and function keys.

- ncurses provides work-alike replacements of SVr4 supplemental libraries based on curses, but which were not specified by X/Open Curses:

  - the panel library, supporting a stack of windows with backing store

  - the menu library, supporting a uniform but flexible interface for menu programming

  - the form library, supporting data collection through on-screen forms

- ncurses's terminal database is fully compatible with that used by SVr4 curses.

  - ncurses supports user-defined capabilities that it can see, but which are hidden from SVr4 curses applications using the same terminal database.

  - It can be optionally configured to match the format used in related systems such as AIX and Tru64.

  - Alternatively, ncurses can be configured to use hashed databases rather than the directory of files used by SVr4 curses.

- The ncurses utilities have options to allow you to filter terminfo entries for use with less capable curses/terminfo versions such as the HP-UX and AIX ports.

The ncurses package also has many useful extensions over SVr4:

- The API is 8-bit clean and base-level conformant with the X/Open Curses specification, XSI curses (that is, it implements all BASE level features, and almost all EXTENDED features). It includes many function calls not supported under SVr4 curses (but portability of all calls is documented so you can use the SVr4 subset only).

- Unlike SVr3 curses, ncurses can write to the rightmost-bottommost corner of the screen if your terminal has an insert-character capability.

- Ada95 and C++ bindings.

- Support for mouse event reporting with X Window xterm and FreeBSD and OS/2 console windows.

- Extended mouse support via Alessandro Rubini's gpm package.

- The function `wresize` allows you to resize windows, preserving their data.

- The function `use_default_colors` allows you to use the terminal's default colors for the default color pair, achieving the effect of transparent colors.

- The functions `keyok` and `define_key` allow you to better control the use of function keys, e.g., disabling the ncurses KEY_MOUSE, or by defining more than one control sequence to map to a given key code.

- Support for direct-color terminals, such as modern xterm.

- Support for 256-color terminals, such as modern xterm.

- Support for 16-color terminals, such as aixterm and modern xterm.

- Better cursor-movement optimization. The package now features a cursor-local-movement computation more efficient than either BSD's or System V's.

- Super hardware scrolling support. The screen-update code incorporates a novel, simple, and cheap algorithm that enables it to make optimal use of hardware scrolling, line-insertion, and line-deletion for screen-line movements. This algorithm is more powerful than the 4.4BSD curses `quickch` routine.

- Real support for terminals with the magic-cookie glitch. The screen-update code will refrain from drawing a highlight if the magic- cookie unattributed spaces required just before the beginning and after the end would step on a non-space character. It will automatically shift highlight boundaries when doing so would make it possible to draw the highlight without changing the visual appearance of the screen.

- It is possible to generate the library with a list of pre-loaded fallback entries linked to it so that it can serve those terminal types even when no terminfo tree or termcap file is accessible (this may be useful for support of screen-oriented programs that must run in single-user mode).

- The tic/captoinfo utility provided with ncurses has the ability to translate many termcaps from the XENIX, IBM and AT&T extension sets.

- A BSD-like tset utility is provided.

- The ncurses library and utilities will automatically read terminfo entries from $HOME/.terminfo if it exists, and compile to that directory if it exists and the user has no write access to the system directory. This feature makes it easier for users to have personal terminfo entries without giving up access to the system terminfo directory.

- You may specify a path of directories to search for compiled descriptions with the environment variable TERMINFO_DIRS (this generalizes the feature provided by TERMINFO under stock System V.)

- In terminfo source files, use capabilities may refer not just to other entries in the same source file (as in System V) but also to compiled entries in either the system terminfo directory or the user's $HOME/.terminfo directory.

- The table-of-entries utility toe makes it easy for users to see exactly what terminal types are available on the system.

- X/Open Curses permits most functions it specifies to be made available as macros as well. ncurses does this

  - to improve performance, e.g., for operations composed of simpler functions such as cursor movement following by adding text to the screen,
  - to simplify the implementation by reusing functions which use common parameters, e.g., the standard screen `stdscr`, and
  - to provide functions that return values via their parameters

  Except for the last case, ncurses provides a non-macro implementation of the function. If the macro definition is disabled with `#undef`, or by defining `NCURSES_NOMACROS` the function may be linked (and its calls will be checked against the prototype).

- Extensive documentation is provided (see the Additional Reading section of the ncurses FAQ for online documentation).

## Applications using ncurses

The ncurses distribution includes a selection of test programs (including a few games). These are available separately as ncurses-examples

The ncurses library has been tested with a wide variety of applications including:

> aptitude

>   FrontEnd to Apt, the debian package manager

>   https://wiki.debian.org/Aptitude

> cdk

>   Curses Development Kit

>   https://invisible-island.net/cdk/

> ded

>   directory-editor

>   https://invisible-island.net/ded/

> dialog

>   the underlying application used in Slackware's setup, and the basis for similar install/configure applications on many systems.

>   https://invisible-island.net/dialog/

> lynx

>   the text WWW browser

>   https://lynx.invisible-island.net/

> mutt

>   mail utility

>   http://www.mutt.org/

> ncftp

>   file-transfer utility

>   https://www.ncftp.com/

> nvi

>   New vi uses ncurses.

>   https://sites.google.com/a/bostic.com/keithbostic/the-berkeley-vi-editor-home-page

> ranger

>   A console file manager with VI key bindings in Python.

>   https://ranger.github.io/

> tin

>   newsreader, supporting color, MIME

>   http://www.tin.org/

> vifm

>   File manager with vi like keybindings

>   https://vifm.info/

as well as some that use ncurses for the terminfo support alone:

> minicom

>   terminal emulator for serial modem connections

>   https://salsa.debian.org/minicom-team/minicom

> mosh

>   a replacement for `ssh`.

>   https://mosh.org/

> tack

>   terminfo action checker

>   https://invisible-island.net/ncurses/tack.html

> tmux

>   terminal multiplexor

>   https://github.com/tmux/tmux/wiki

> vile

>   vi-like-emacs may be built to use the terminfo, termcap or curses interfaces.

>   https://invisible-island.net/vile/

and finally, those which use only the termcap interface:

> emacs

>   text editor

>   https://www.gnu.org/software/emacs/

> less

>   The most commonly used pager (a program that displays text files).

>   http://www.greenwoodsoftware.com/less/

> screen

>   terminal multiplexor

>   https://www.gnu.org/software/screen/

> vim

>   text editor

>   https://www.vim.org/

## Development activities

Zeyd Ben-Halim started ncurses from a previous package pcurses, written by Pavel Curtis. Eric S. Raymond continued development. Jürgen Pfeifer wrote most of the form and menu libraries.

Ongoing development work is done by Thomas E. Dickey. Thomas E. Dickey has acted as the maintainer for the Free Software Foundation, which held a copyright on ncurses for releases 4.2 through 6.1. Following the release of ncurses 6.1, effective as of release 6.2, copyright for ncurses reverted to Thomas E. Dickey (see the ncurses FAQ for additional information).

Contact the current maintainers at

> bug-ncurses@gnu.org

To join the ncurses mailing list, please write email to

> bug-ncurses-request@gnu.org

containing the line:

> `subscribe` <name>@<host.domain>

This list is open to anyone interested in helping with the development and testing of this package.

Beta versions of ncurses are made available at

> https://invisible-island.net/archives/ncurses/current/ and
> https://invisible-mirror.net/archives/ncurses/current/ .

Patches to the current release are made available at

> https://invisible-island.net/archives/ncurses/6.4/ and
> https://invisible-mirror.net/archives/ncurses/6.4/ .

There is an archive of the mailing list here:

> https://lists.gnu.org/archive/html/bug-ncurses .

## Related resources

The release notes make scattered references to these pages, which may be interesting by themselves:

- ncurses licensing
- Symbol versioning in ncurses
- Comments on ncurses versus slang (S-Lang)
- Comments on OpenBSD
- tack – terminfo action checker
- tctest – termcap library checker
- Terminal Database

## Other resources

The distribution provides a newer version of the terminfo-format terminal description file once maintained by Eric Raymond . Unlike the older version, the termcap and terminfo data are provided in the same file, which also provides several user-definable extensions beyond the X/Open Curses specification.

You can find lots of information on terminal-related topics not covered in the terminfo file in Richard Shuford's archive (original). The collection of computer manuals at bitsavers.org has also been useful.