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:
The distribution includes the library and support utilities, including
Full manual pages are provided for the library and tools.
The ncurses distribution is available at ncurses' homepage:
ftp://ftp.invisible-island.net/ncurses/ or
https://invisible-mirror.net/archives/ncurses/ .
It is also available via anonymous FTP at the GNU distribution site
These notes are for ncurses 6.2, released February 12, 2020.
This release is designed to be source-compatible with ncurses 5.0 through 6.1; 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 user-defined capabilities in terminal descriptions. The release notes also mention some other bug-fixes, but are focused on new features and improvements to existing features since ncurses 6.1 release.
There are several new features:
O_EDGE_INSERT_STAY tells the form library to optionally delay cursor movement on a field edge/boundary
O_INPUT_FIELD extension to form library allows a dynamic field to shrink if the new limit is smaller than the current field size.
added exit_curses and exit_terminfo to replace internal symbols for leak-checking.
added curses_trace, to replace trace().
Additionally, to improve performance other changes (and extensions) are provided in this release:
mouse decoding now handles shift/control/alt logic when decoding xterm's 1006 mode
ncurses now defines a limit for wgetnstr, wgetn_wstr when length is negative or “too large”.
there is now no buffer-size limit when reading the $TERMCAP variable.
the $TERMCAP variable may be interpreted as a fallback to a terminfo entry
mvcur now decides whether to use hard-tabs, using xt, tbc and hts as clues.
extended colors are improved by modifying an internal call to vid_puts to pass extended color pairs e.g., from tty_update.c and lib_mvcur.c
the initialization functions now avoid relying upon persistent data for the result from getenv
scrolling is improved:
improved loop limits in _nc_scroll_window handle a case where the scrolled data is a pad which is taller than the window.
These are revised features:
used “const” in some prototypes rather than NCURSES_CONST where X/Open Curses was updated to do this, e.g., wscanw, newterm, the terminfo interface. Also use “const” for consistency in the termcap interface, which was withdrawn by X/Open Curses in Issue 5 (2007). As of Issue 7, X/Open Curses still lacks “const” for certain return values, e.g., keyname.
modified wbkgd and wbkgrnd to improve compatibility with SVr4 curses, changing the way the window rendition is updated when the background character is modified
improved terminfo write/read by modifying the fourth item of the extended header to denote the number of valid strings in the extended string table (see term(5)).
modified the initialization checks for mouse so that the xterm+sm+1006 block will work with terminal descriptions not mentioning xterm.
These were done to limit or ultimately deprecate features:
deprecated safe-sprintf, since the vsnprintf function, which does what was needed, was standardized long ago.
marked vwprintw and vwscanw as deprecated; recommend using vw_printw and vw_scanw, respectively.
added deprecation warnings for internal functions called by older versions of tack.
removed unused _nc_import_termtype2 function.
These are improvements to existing features:
check parameter of set_escdelay, return ERR if negative.
check parameter of set_tabsize, return ERR if not greater than zero
correct a status-check in _nc_read_tic_entry() so that if reading a hex/b64 $TERMINFO, and the $TERM does not match, fall-through to the compiled-in search list.
amend check for repeat_char to handle a case where setlocale() was called after initscr
move macro for is_linetouched inside NCURSES_NOMACROS ifndef.
use _nc_copy_termtype2 rather than direct assignment in setupterm, in case it is called repeatedly using fallback terminfo descriptions
improve workaround for Solaris wcwidth versus line-drawing characters
add checks in repair_subwindows to keep the current position and scroll-margins inside the resized subwindow.
correct a buffer-limit in write_entry.c for systems that use caseless filenames.
improved build-time utility report_offsets:
add categories, e.g., "w" for wide-character, "t" for threads to make the report more readable. Reorganized the structures reported to make the categories more apparent.
add NCURSES_GLOBALS and NCURSES_PRESCREEN to report to show how similar the different libtinfo configurations are.
modified some header files to ensure that those include necessary files except for the previously-documented cases
added some traces in initialization to show whether a fallback entry is used.
made minor optimization to reduce calls to _nc_reserve_pairs
These are corrections to existing features:
fix a special case in PutAttrChar where a cell is marked as alternate-character set, but the terminal does not actually support the given graphic character. This would happen in an older terminal such as vt52, which lacks most line-drawing capability.
corrected flag for "seq" method of db 1.8.5 interface, needed by toe on some of the BSDs.
modify comparison in make_hash.c to correct a special case in collision handling for Caps-hpux11
add extended_slk_color{,_sp} symbols to the appropriate package/*.{map,sym} files
modify lib_setup to avoid calling pthread_self() without first verifying that the address is valid, i.e., for weak symbols
add a couple of broken-linker symbols to the list of versioned symbols to help with link-time optimization versus weak symbols.
Several improvements were made to the utility programs:
Several changes were made to the generated ncurses*config scripts and the analogous “.pc” files to reduce differences between the configurations they report:
modified the ncurse*-config and pc-files to more closely match for the -I and -l options.
filtered out linker-specs from the --libs report.
amended the ncurses*-config and pc-files to take into account the rpath hack which differed between those files.
modified generated ncurses*config and ncurses.pc, ncursesw.pc, etc., to list helper libraries such as gpm for static linking.
Along with the library and utilities, improvements were made to the ncurses-examples. Most of this activity aimed at improving the test-packages. A few changes are more generally useful, e.g., for the main ncurses test-program, and for analyzing traces using the tracemunch script:
improve recovery from error when reading command-character in test/ncurses.c, showing the relevant error message and not exiting on EINTR.
improve tracemunch, by keeping track of TERMINAL* values, and if tracing was first turned on after initialization, attempt to show distinct screen, window and terminal names anyway.
modify tracemunch to accept filename parameters in addition to use as a pipe/filter.
update tracemunch to work with perl 5.26.2, which changed the rules for escaping regular expressions.
add some checks in tracemunch for undefined variables.
modify TurnOn/TurnOff macros (in lib_vidattr.c and lib_vid_attr.c) to avoid expansion of “CUR” in trace.
There are other new demo/test programs and reusable examples:
A variety of improvements were made to existing programs, both new features as well as options added to make the set of programs more consistent.
add “-l” option to test/background, to dump screen contents in a form that lets different curses implementations be compared.
add “@” command to test/ncurses F-test, to allow rapid jump to different character pages.
added enum, regex examples to test/demo_forms
amend Scaled256() macro in test/picsmap.c to cover the full range 0..1000
corrected pathname used in Ada95 sample programs for explain.txt, to work with test-packages, and used an awk script to split the resulting pathname when it would be too long for a single line.
ignore interrupted system-call in test/ncurses's command-line, e.g., if the terminal were resized.
improved ifdef's for TABSIZE variable, to help with AIX/HPUX ports.
There are several new terminal descriptions:
alacritty, domterm, kitty, mintty, mintty-direct, ms-terminal, n7900, nsterm-build309, nsterm-direct, screen5, ti703, ti707, ti703-w, ti707-w vscode, vscode-direct, xterm-mono, xterm.js
There are many changes to existing terminal descriptions. Some were updates to several descriptions:
while others affected specific descriptions. These were retested, to take into account changes by their developers:
terminator, st
while these are specific fixes based on reviewing documentation, user reports, or warnings from tic:
A few entries use extensions (user-defined terminal capabilities):
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:
Clarify in manual pages that
vwprintw and
vwscanw are obsolete.
They have not been part of X/Open Curses since 2007.
New/improved history and portability sections:
Improvements for user_caps.5:
Other improvements:
There are no new manual pages (all of the manual page updates are to existing pages).
Some of the improvements are more subtle, relating to the way the information is presented. For instance, the generated terminfo.5 file uses a different table layout, allowing it to use space on wide terminals more effectively.
While there were many bugs fixed during development of ncurses 6.2, only a few (the reason for this release) were both important and interesting. Most of the bug-fixes were for local issues which did not affect compatibility across releases. Since those are detailed in the NEWS file no elaboration is needed here.
The interesting bugs were in tic/infocmp's handling of user-defined capabilities. These were not recent bugs. Initially it was a simple problem:
One of simpleterm's contributors copied some definitions for using tmux's user-defined capabilities in late in 2016.
diff --git a/st.info b/st.info @@ -185,7 +185,10 @@ st| simpleterm, tsl=\E]0;, xenl, vpa=\E[%i%p1%dd, - +# Tmux unofficial extensions, see TERMINFO EXTENSIONS in tmux(1) + Se, + Ss, + Tc, st-256color| simpleterm with 256 colors, use=st,
Later, in (referring to a version from mid-2017), a user asked to have it updated in ncurses.
However, it had an error from the change in late 2016. The terminal description made what tmux expected to be string actually a boolean.
Over the years, there were problems with each of simpleterm's terminal descriptions. I repaired those, and usually dealt with the problem.
The difference in this case was that when compiling the terminal database, tic may have in memory the definitions for more than one terminal description (so that it can resolve “use=” clauses). Seeing two different types for the same name, in certain situations it would incorrectly merge the symbol tables for the two terminal descriptions.
On simpleterm's side, their bug was finally fixed in late 2019, three years after the bug was created.
For ncurses, the elapsed time to fix this bug was less than three years. Someone reported a problem with the terminal description a few weeks after releasing ncurses 6.1 (in tmux #1264), and the terminal description was updated that week (ncurses patch 20180224):
20180224
+ modify _nc_resolve_uses2() to detect incompatible types when merging
a "use=" clause of extended capabilities. The problem was seen in a
defective terminfo integrated from simpleterm sources in 20171111,
compounded by repair in 20180121.
+ correct Ss/Ms interchange in st-0.7 entry (tmux #1264) -TD
The larger part of that change added a check to prevent a simple merge of terminal descriptions where the same user-defined name was used with different types. But it raised some questions:
Was there a reliable way to manage terminal descriptions which used the same extended name in different ways?
Should ncurses provide a registry of well-known extended names, with their types?
Since the correction to terminfo.src could have been readily adopted by packagers, there was nothing more to be done from ncurses' standpoint on that part. But improving ncurses to prevent issues like that is the reason for making a release.
Nothing more (constructive) was mentioned with regard to simpleterm. But a few problems were found in the handling of user-defined capabilities:
Forward-references to user-defined capabilities in a “use=” clause did not allocate new data for each use. In tic, successive compilation of terminal entries could add user-defined capabilities to the wrong terminal entry.
This was not noticed before, since xterm's terminal descriptions were the main users of the feature, and almost all of the uses of the building-blocks which contained user-defined capabilities were backward-references.
There is one (documented) case where ncurses 6.1 supports a user-defined capability that could be any type (i.e., “RGB”). The check added in February 2018 to guard against mismatches did not handle all of the combinations needed.
Both of these issues dated from the original implementation of user-defined capabilities. Fixing them does not change the terminal database, but a older tic without the fixes will not be able to handle terminfo sources which rely upon those fixes. Starting in June 2019, the download link for the terminfo source file was capped at that date. The development sources have an up-to-date copy of the file, for people with a legitimate need for it.
The “-c” (check) option of tic is not very useful if it cannot offer advice on parameters needed for user-defined capabilities. The various Caps files were reorganized to reduce redundancy, and in the common portion (Caps-ncurses), a registry of user-defined capabilities is provided for use by tic. While users can still define their own custom capabilities, tic will not offer any advice when their parameters do not match.
In ncurses 6.2, tic makes a special check to allow any type for RGB, but its being able to do this relies upon fixes made in the ncurses library in mid-2019.
There are no major changes. Several new options were added to ease integration of packages with systems using different versions of GNAT and ncurses. Also, improvements were made to configure checks.
There are a few new/modified configure options:
helps work around a filename conflict with Debian packages versus test-packages.
allows one to rename the “AdaCurses” library (at least one packager prefers a lowercase name).
now ensures there is a value, and adds the fallback information to top-level Makefile summary.
check for pcre-posix library to help with MinGW port.
help work around problems building fallback source using pre-6.0 tic/infocmp.
option value can now be a relative pathname.
Many of the portability changes are implemented via the configure script:
ignore $TERMINFO as a default value in configure script if it came from the infocmp -Q option.
distinguish gcc from icc and clang when the --enable-warnings option is not used, to avoid unnecessary warnings about unrecognized inline options
consistently prepend new libraries as they are found during configuration, rather than relying upon the linker to resolve order dependencies of libraries.
modified configure scripts to reduce relinking/ranlib during library install :
add configure check for getenv to work around implementation shown in Emscripten which overwrites the previous return value on each call.
Use that to optionally suppress START_TRACE macro, whose call to getenv may not work properly
change target configure level for _XOPEN_SOURCE to 600 to address use of vsscanf and setenv.
reduce use of _GNU_SOURCE for current glibc where _DEFAULT_SOURCE combines with _XOPEN_SOURCE
Allow for Cygwin's newlib when checking for the _DEFAULT_SOURCE symbol.
MidnightBSD is now checked for the _XOPEN_SOURCE-related definitions.
If the check for va_copy or __va_copy fails,
several changes to support a port to Ultrix 3.1:
The test/configure script (used for ncurses-examples) is improved:
Here are some of the other portability fixes:
added dummy "check" rule in top-level and test-Makefile to simplify building test-packages for ArchLinux.
dropped library-dependency on psapi for MinGW port, since win_driver.c defines PSAPI_VERSION to 2, making it use GetProcessImageFileName from kernel32.dll
made build-fixes for configuration using --program-suffix with Ada95, noticed with MacOS but applicable to other platforms without libpanelw, etc.
modified ncurses/Makefile.in to fix a case where Debian/testing changes to the ld --as-needed configuration broke ncurses-examples test packages.
used _WIN32/_WIN64 in preference to __MINGW32__/__MINGW64__ symbols to simplify building with Microsoft Visual C++, since the former are defined in both compiler configurations.
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 all of the for SVr4 curses features including keyboard mapping, color, forms-drawing with ACS characters, and automatic recognition of keypad and function keys.
ncurses provides these SVr4 add-on libraries (not part of X/Open Curses):
the panels library, supporting a stack of windows with backing store.
the menus 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 which 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 most 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 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.
The library meets the XSI requirement that every macro
entry point have a corresponding function which may be linked
(and will be prototype-checked) if the macro definition is
disabled with #undef.
Extensive documentation is provided (see the Additional Reading section of the ncurses FAQ for online documentation).
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
- cdk
Curses Development Kit
- ded
directory-editor
- dialog
the underlying application used in Slackware's setup, and the basis for similar install/configure applications on many systems.
- lynx
the text WWW browser
- mutt
mail utility
- ncftp
file-transfer utility
- nvi
New vi uses ncurses.
- ranger
A console file manager with VI key bindings in Python.
- tin
newsreader, supporting color, MIME
- vifm
File manager with vi like keybindings
as well as some that use ncurses for the terminfo support alone:
- minicom
terminal emulator for serial modem connections
- mosh
a replacement for
ssh.- tack
terminfo action checker
- tmux
terminal multiplexor
- vile
vi-like-emacs may be built to use the terminfo, termcap or curses interfaces.
and finally, those which use only the termcap interface:
- emacs
text editor
- less
The most commonly used pager (a program that displays text files).
- screen
terminal multiplexor
- vim
text editor
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 holds 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.orgcontaining 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
ftp://ftp.invisible-island.net/ncurses/current/ and
https://invisible-mirror.net/archives/ncurses/current/ .
Patches to the current release are made available at
ftp://ftp.invisible-island.net/ncurses/6.1/ and
https://invisible-mirror.net/archives/ncurses/6.1/ .
There is an archive of the mailing list here:
The release notes make scattered references to these pages, which may be interesting by themselves:
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 specification.
You can find lots of information on terminal-related topics not covered in the terminfo file at Richard Shuford's archive . The collection of computer manuals at bitsavers.org has also been useful.