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download PDF document: curses.3x.pdf

ncurses(3X) Library calls ncurses(3X)
NAME ncurses - character-cell terminal interface with optimized output
SYNOPSIS #include <curses.h>
DESCRIPTION The "new curses" library offers the programmer a terminal-independent means of reading keyboard and mouse input and updating character-cell terminals with output optimized to minimize screen updates. ncurses replaces the curses libraries from System V Release 4 Unix ("SVr4") and 4.4BSD Unix, the development of which ceased in the 1990s. This document describes ncurses version 6.5 (patch 20240427).
ncurses permits control of the terminal screen's contents; abstraction and subdivision thereof with windows and pads; the reading of terminal input; control of terminal input and output options; environment query routines; color manipulation; the definition and use of soft label keys; terminfo capability access; a termcap compatibility interface; and an abstraction of the system's API for manipulating the terminal (such as termios(3)).
ncurses implements the standard interface described by X/Open Curses Issue 7. In many behavioral details not standardized by X/Open, ncurses emulates the curses library of SVr4 and provides numerous useful extensions.
ncurses man pages employ several sections to clarify matters of usage and interoperability with other curses implementations.
o "NOTES" describes issues and caveats of which any user of the ncurses API should be aware, such as limitations on the size of an underlying integral type or the availability of a preprocessor macro exclusive of a function definition (which prevents its address from being taken). This section also describes implementation details that will be significant to the programmer but which are not standardized.
o "EXTENSIONS" presents ncurses innovations beyond the X/Open Curses standard and/or the SVr4 curses implementation. They are termed extensions to indicate that they cannot be implemented solely by using the library API, but require access to the library's internal state.
o "PORTABILITY" discusses matters (beyond the exercise of extensions) that should be considered when writing to a curses standard, or for multiple implementations.
o "HISTORY" examines points of detail in ncurses and other curses implementations over the decades of their development, particularly where precedent or inertia have frustrated better design (and, in a few cases, where such inertia has been overcome).
A curses application must be linked with the library; use the -lncurses option to your compiler or linker. A debugging version of the library may be available; if so, link with it using -lncurses_g. (Your system integrator may have installed these libraries such that you can use the setlocale(3) prepares it for curses library calls.
setlocale(LC_ALL, "");
If the locale is not thus initialized, the library assumes that characters are printable as in ISO 8859-1, to work with certain legacy programs. You should initialize the locale; do not expect consistent behavior from the library when the locale has not been set up.
initscr(3X) or newterm(3X) must be called to initialize curses before use of any functions that deal with windows and screens.
To get character-at-a-time input without echoing--most interactive, screen-oriented programs want this--use the following sequence.
initscr(); cbreak(); noecho();
Most applications perform further setup as follows.
intrflush(stdscr, FALSE); keypad(stdscr, TRUE);
A curses program then often enters an event loop of some sort. Call endwin(3X) before exiting.
Overview A curses library abstracts the terminal screen by representing all or part of it as a WINDOW data structure. A window is a rectangular grid of character cells, addressed by row and column coordinates (y, x), with the upper left corner as (0, 0). A window called stdscr, the same size as the terminal screen, is always available. Create others with newwin(3X).
A curses library does not manage overlapping windows (but see below). You can either use stdscr to manage one screen-filling window, or tile the screen into non-overlapping windows and not use stdscr at all. Mixing the two approaches will result in unpredictable and undesired effects.
Functions permit manipulation of a window and the cursor identifying the cell within it at which the next output operation will occur. Among those, the most basic are move(3X) and addch(3X): these place the cursor and write a character to stdscr, respectively.
Frequent changes to the terminal screen can cause unpleasant flicker or inefficient use of the communication channel to the device, so the library does not generally update it automatically. Therefore, after using curses functions to accumulate a set of desired updates that make sense to present together, call refresh(3X) to tell the library to make the user's screen look like stdscr. The library optimizes its output by computing a minimal number of operations to mutate the screen from its state at the previous refresh to the new one. Effective optimization demands accurate information about the terminal device: the management of such information is the province of the terminfo(3X) API, a feature of every standard curses implementation.
Special windows called pads may also be manipulated. These are windows that are not constrained to the size of the terminal screen and whose contents need not be completely displayed. See curs_pad(3X). corresponding to the DEC Alternate Character Set (ACS), a feature of VT100 and other terminals. See waddch(3X).
curses is implemented using the operating system's terminal driver; keystroke events are received not as scan codes but as byte sequences. Graphical keycaps (alphanumeric and punctuation keys, and the space) appear as-is. Everything else, including the tab, enter/return, keypad, arrow, and function keys, appears as a control character or a multibyte escape sequence. curses translates these into unique key codes. See getch(3X).
ncurses provides reimplementations of the SVr4 panel(3X), form(3X), and menu(3X) libraries to ease construction of user interfaces with curses.
Initialization The selection of an appropriate value of TERM in the process environment is essential to correct curses and terminfo library operation. A well-configured system selects a correct TERM value automatically; tset(1) may assist with troubleshooting exotic situations.
If you change the terminal type, export the TERM environment variable in the shell, then run tset(1) or the "tput init" command. See subsection "Tabs and Initialization" of terminfo(5).
If the environment variables LINES and COLUMNS are set, or if the curses program is executing in a graphical windowing environment, the information obtained thence overrides that obtained by terminfo. An ncurses extension supports resizable terminals; see wresize(3X).
If the environment variable TERMINFO is defined, a curses program checks first for a terminal type description in the location it identifies. TERMINFO is useful for developing experimental type descriptions or when write permission to /usr/share/misc/terminfo is not available.
See section "ENVIRONMENT" below.
Naming Conventions curses offers many functions in variant forms using a regular set of alternatives to the name of an elemental one. Those prefixed with "w" require a WINDOW pointer argument; those with a "mv" prefix first perform cursor movement using wmove(3X); a "mvw" prefix indicates both. The "w" function is typically the elemental one; the removal of this prefix usually indicates operation on stdscr.
Four functions prefixed with "p" require a pad argument.
In function synopses, ncurses man pages apply the following names to parameters.
bf bool (TRUE or FALSE) c a char or int ch a chtype wc a wchar_t or wint_t wch a cchar_t win pointer to a WINDOW pad pointer to a WINDOW that is a pad
attributes in a chtype datum, which is often an alias of int.
Attributes alone (with no corresponding character) can be stored in variables of chtype or attr_t type. In either case, they are represented as an integral bit mask.
Each cell of a WINDOW is stored as a chtype.
ncursesw is the library in its "wide" configuration, which handles character encodings requiring a larger data type than char (a byte-sized type) can represent. It adds about one third more calls using additional data types that can store such multibyte characters.
cchar_t corresponds to the non-wide configuration's chtype. It always a structure type, because it stores more data than fit into a standard scalar type. A character code may not be representable as a char, and moreover more than one character may occupy a cell (as with accent marks and other diacritics). Each character is of type wchar_t; a complex character contains one spacing character and zero or more non-spacing characters (see below). Attributes and color data are stored in separate fields of the structure, not combined as in chtype.
Each cell of a WINDOW is stored as a cchar_t.
setcchar(3X) and getcchar(3X) store and retrieve cchar_t data. The wide library API of ncurses depends on two data types standardized by ISO C95.
wchar_t stores a wide character. Like chtype, it may be an alias of int. Depending on the character encoding, a wide character may be spacing, meaning that it occupies a character cell by itself and typically accompanies cursor advancement, or non-spacing, meaning that it occupies the same cell as a spacing character, is often regarded as a "modifier" of the base glyph with which it combines, and typically does not advance the cursor.
wint_t can store a wchar_t or the constant WEOF, analogously to the int-sized character manipulation functions of ISO C and its constant EOF.
The wide library provides additional functions that complement those in the non-wide library where the size of the underlying character type is significant. A somewhat regular naming convention relates many of the wide variants to their non-wide counterparts; where a non-wide function name contains "ch" or "str", prefix it with "_w" to obtain the wide counterpart. For example, waddch becomes wadd_wch. (Exceptions that add only "w" comprise addwstr, inwstr, and their variants.)
This convention is inapplicable to some non-wide function names, so other transformations are used for the wide configuration: the window background management function
and wide APIs and the corresponding man pages that describe them. Those flagged with "*" are ncurses-specific, neither described by X/Open Curses nor present in SVr4.
ccuurrsseess Function Name Man Page --------------------------------------------- COLOR_PAIR curs_color(3X) PAIR_NUMBER curs_color(3X) add_wch curs_add_wch(3X) add_wchnstr curs_add_wchstr(3X) add_wchstr curs_add_wchstr(3X) addch curs_addch(3X) addchnstr curs_addchstr(3X) addchstr curs_addchstr(3X) addnstr curs_addstr(3X) addnwstr curs_addwstr(3X) addstr curs_addstr(3X) addwstr curs_addwstr(3X) alloc_pair new_pair(3X)* assume_default_colors default_colors(3X)* attr_get curs_attr(3X) attr_off curs_attr(3X) attr_on curs_attr(3X) attr_set curs_attr(3X) attroff curs_attr(3X) attron curs_attr(3X) attrset curs_attr(3X) baudrate curs_termattrs(3X) beep curs_beep(3X) bkgd curs_bkgd(3X) bkgdset curs_bkgd(3X) bkgrnd curs_bkgrnd(3X) bkgrndset curs_bkgrnd(3X) border curs_border(3X) border_set curs_border_set(3X) box curs_border(3X) box_set curs_border_set(3X) can_change_color curs_color(3X) cbreak curs_inopts(3X) chgat curs_attr(3X) clear curs_clear(3X) clearok curs_outopts(3X) clrtobot curs_clear(3X) clrtoeol curs_clear(3X) color_content curs_color(3X) color_set curs_attr(3X) copywin curs_overlay(3X) curs_set curs_kernel(3X) curses_trace curs_trace(3X)* curses_version curs_extend(3X)* def_prog_mode curs_kernel(3X) def_shell_mode curs_kernel(3X) define_key define_key(3X)* del_curterm curs_terminfo(3X) delay_output curs_util(3X) delch curs_delch(3X) deleteln curs_deleteln(3X) delscreen curs_initscr(3X) delwin curs_window(3X) erase curs_clear(3X) erasechar curs_termattrs(3X) erasewchar curs_termattrs(3X) exit_curses curs_memleaks(3X)* exit_terminfo curs_memleaks(3X)* extended_color_content curs_color(3X)* extended_pair_content curs_color(3X)* extended_slk_color curs_slk(3X)* filter curs_util(3X) find_pair new_pair(3X)* flash curs_beep(3X) flushinp curs_util(3X) free_pair new_pair(3X)* get_escdelay curs_threads(3X)* get_wch curs_get_wch(3X) get_wstr curs_get_wstr(3X) getattrs curs_attr(3X) getbegx curs_legacy(3X)* getbegy curs_legacy(3X)* getbegyx curs_getyx(3X) getbkgd curs_bkgd(3X) getbkgrnd curs_bkgrnd(3X) getcchar curs_getcchar(3X) getch curs_getch(3X) getcurx curs_legacy(3X)* getcury curs_legacy(3X)* getmaxx curs_legacy(3X)* getmaxy curs_legacy(3X)* getmaxyx curs_getyx(3X) getmouse curs_mouse(3X)* getn_wstr curs_get_wstr(3X) getnstr curs_getstr(3X) getparx curs_legacy(3X)* getpary curs_legacy(3X)* getparyx curs_getyx(3X) getstr curs_getstr(3X) getsyx curs_kernel(3X) getwin curs_util(3X) getyx curs_getyx(3X) halfdelay curs_inopts(3X) has_colors curs_color(3X) has_ic curs_termattrs(3X) has_il curs_termattrs(3X) has_key curs_getch(3X)* has_mouse curs_mouse(3X)* hline curs_border(3X) hline_set curs_border_set(3X) idcok curs_outopts(3X) idlok curs_outopts(3X) immedok curs_outopts(3X) in_wch curs_in_wch(3X) in_wchnstr curs_in_wchstr(3X) in_wchstr curs_in_wchstr(3X) inch curs_inch(3X) inchnstr curs_inchstr(3X) inchstr curs_inchstr(3X) init_color curs_color(3X) init_extended_color curs_color(3X)* init_extended_pair curs_color(3X)* insch curs_insch(3X) insdelln curs_deleteln(3X) insertln curs_deleteln(3X) insnstr curs_insstr(3X) insstr curs_insstr(3X) instr curs_instr(3X) intrflush curs_inopts(3X) inwstr curs_inwstr(3X) is_cbreak curs_inopts(3X)* is_cleared curs_opaque(3X)* is_echo curs_inopts(3X)* is_idcok curs_opaque(3X)* is_idlok curs_opaque(3X)* is_immedok curs_opaque(3X)* is_keypad curs_opaque(3X)* is_leaveok curs_opaque(3X)* is_linetouched curs_touch(3X) is_nl curs_inopts(3X)* is_nodelay curs_opaque(3X)* is_notimeout curs_opaque(3X)* is_pad curs_opaque(3X)* is_raw curs_inopts(3X)* is_scrollok curs_opaque(3X)* is_subwin curs_opaque(3X)* is_syncok curs_opaque(3X)* is_term_resized resizeterm(3X)* is_wintouched curs_touch(3X) isendwin curs_initscr(3X) key_defined key_defined(3X)* key_name curs_util(3X) keybound keybound(3X)* keyname curs_util(3X) keyok keyok(3X)* keypad curs_inopts(3X) killchar curs_termattrs(3X) killwchar curs_termattrs(3X) leaveok curs_outopts(3X) longname curs_termattrs(3X) mcprint curs_print(3X)* meta curs_inopts(3X) mouse_trafo curs_mouse(3X)* mouseinterval curs_mouse(3X)* mousemask curs_mouse(3X)* move curs_move(3X) mvadd_wch curs_add_wch(3X) mvadd_wchnstr curs_add_wchstr(3X) mvadd_wchstr curs_add_wchstr(3X) mvaddch curs_addch(3X) mvaddchnstr curs_addchstr(3X) mvaddchstr curs_addchstr(3X) mvaddnstr curs_addstr(3X) mvaddnwstr curs_addwstr(3X) mvaddstr curs_addstr(3X) mvaddwstr curs_addwstr(3X) mvchgat curs_attr(3X) mvcur curs_terminfo(3X) mvdelch curs_delch(3X) mvderwin curs_window(3X) mvget_wch curs_get_wch(3X) mvin_wch curs_in_wch(3X) mvin_wchnstr curs_in_wchstr(3X) mvin_wchstr curs_in_wchstr(3X) mvinch curs_inch(3X) mvinchnstr curs_inchstr(3X) mvinchstr curs_inchstr(3X) mvinnstr curs_instr(3X) mvinnwstr curs_inwstr(3X) mvins_nwstr curs_ins_wstr(3X) mvins_wch curs_ins_wch(3X) mvins_wstr curs_ins_wstr(3X) mvinsch curs_insch(3X) mvinsnstr curs_insstr(3X) mvinsstr curs_insstr(3X) mvinstr curs_instr(3X) mvinwstr curs_inwstr(3X) mvprintw curs_printw(3X) mvscanw curs_scanw(3X) mvvline curs_border(3X) mvvline_set curs_border_set(3X) mvwadd_wch curs_add_wch(3X) mvwadd_wchnstr curs_add_wchstr(3X) mvwadd_wchstr curs_add_wchstr(3X) mvwaddch curs_addch(3X) mvwaddchnstr curs_addchstr(3X) mvwaddchstr curs_addchstr(3X) mvwaddnstr curs_addstr(3X) mvwaddnwstr curs_addwstr(3X) mvwaddstr curs_addstr(3X) mvwaddwstr curs_addwstr(3X) mvwchgat curs_attr(3X) mvwdelch curs_delch(3X) mvwget_wch curs_get_wch(3X) mvwget_wstr curs_get_wstr(3X) mvwgetch curs_getch(3X) mvwgetn_wstr curs_get_wstr(3X) mvwgetnstr curs_getstr(3X) mvwgetstr curs_getstr(3X) mvwhline curs_border(3X) mvwhline_set curs_border_set(3X) mvwin curs_window(3X) mvwin_wch curs_in_wch(3X) mvwin_wchnstr curs_in_wchstr(3X) mvwin_wchstr curs_in_wchstr(3X) mvwinch curs_inch(3X) mvwinchnstr curs_inchstr(3X) mvwinchstr curs_inchstr(3X) mvwinnstr curs_instr(3X) mvwinnwstr curs_inwstr(3X) mvwins_nwstr curs_ins_wstr(3X) mvwins_wch curs_ins_wch(3X) mvwins_wstr curs_ins_wstr(3X) mvwinsch curs_insch(3X) mvwinsnstr curs_insstr(3X) mvwinsstr curs_insstr(3X) mvwinstr curs_instr(3X) mvwinwstr curs_inwstr(3X) mvwprintw curs_printw(3X) mvwscanw curs_scanw(3X) nocbreak curs_inopts(3X) nodelay curs_inopts(3X) noecho curs_inopts(3X) nofilter curs_util(3X)* nonl curs_inopts(3X) noqiflush curs_inopts(3X) noraw curs_inopts(3X) notimeout curs_inopts(3X) overlay curs_overlay(3X) overwrite curs_overlay(3X) pair_content curs_color(3X) pecho_wchar curs_pad(3X) pechochar curs_pad(3X) pnoutrefresh curs_pad(3X) prefresh curs_pad(3X) printw curs_printw(3X) putp curs_terminfo(3X) putwin curs_util(3X) qiflush curs_inopts(3X) raw curs_inopts(3X) redrawwin curs_refresh(3X) refresh curs_refresh(3X) reset_color_pairs curs_color(3X)* reset_prog_mode curs_kernel(3X) reset_shell_mode curs_kernel(3X) resetty curs_kernel(3X) resize_term resizeterm(3X)* resizeterm resizeterm(3X)* restartterm curs_terminfo(3X) ripoffline curs_kernel(3X) savetty curs_kernel(3X) scanw curs_scanw(3X) scr_dump curs_scr_dump(3X) scr_init curs_scr_dump(3X) scr_restore curs_scr_dump(3X) scr_set curs_scr_dump(3X) scrl curs_scroll(3X) scroll curs_scroll(3X) scrollok curs_outopts(3X) set_curterm curs_terminfo(3X) set_escdelay curs_threads(3X)* set_tabsize curs_threads(3X)* set_term curs_initscr(3X) setcchar curs_getcchar(3X) setscrreg curs_outopts(3X) setsyx curs_kernel(3X) setupterm curs_terminfo(3X) slk_attr curs_slk(3X)* slk_attr_off curs_slk(3X) slk_attr_on curs_slk(3X) slk_attr_set curs_slk(3X) slk_attroff curs_slk(3X) slk_attron curs_slk(3X) slk_attrset curs_slk(3X) slk_clear curs_slk(3X) slk_color curs_slk(3X) slk_init curs_slk(3X) slk_label curs_slk(3X) slk_noutrefresh curs_slk(3X) start_color curs_color(3X) subpad curs_pad(3X) subwin curs_window(3X) syncok curs_window(3X) term_attrs curs_termattrs(3X) termattrs curs_termattrs(3X) termname curs_termattrs(3X) tgetent curs_termcap(3X) tgetflag curs_termcap(3X) tgetnum curs_termcap(3X) tgetstr curs_termcap(3X) tgoto curs_termcap(3X) tigetflag curs_terminfo(3X) tigetnum curs_terminfo(3X) tigetstr curs_terminfo(3X) timeout curs_inopts(3X) tiparm curs_terminfo(3X) tiparm_s curs_terminfo(3X)* tiscan_s curs_terminfo(3X)* touchline curs_touch(3X) touchwin curs_touch(3X) tparm curs_terminfo(3X) tputs curs_termcap(3X) tputs curs_terminfo(3X) trace curs_trace(3X)* typeahead curs_inopts(3X) unctrl curs_util(3X) unget_wch curs_get_wch(3X) ungetch curs_getch(3X) ungetmouse curs_mouse(3X)* untouchwin curs_touch(3X) use_default_colors default_colors(3X)* use_env curs_util(3X) use_extended_names curs_extend(3X)* use_legacy_coding legacy_coding(3X)* use_screen curs_threads(3X)* use_tioctl curs_util(3X)* use_window curs_threads(3X)* vid_attr curs_terminfo(3X) vid_puts curs_terminfo(3X) vidattr curs_terminfo(3X) vidputs curs_terminfo(3X) vline curs_border(3X) vline_set curs_border_set(3X) vw_printw curs_printw(3X) vw_scanw curs_scanw(3X) vwprintw curs_printw(3X) vwscanw curs_scanw(3X) wadd_wch curs_add_wch(3X) wadd_wchnstr curs_add_wchstr(3X) wadd_wchstr curs_add_wchstr(3X) waddch curs_addch(3X) waddchnstr curs_addchstr(3X) waddchstr curs_addchstr(3X) waddnstr curs_addstr(3X) waddnwstr curs_addwstr(3X) waddstr curs_addstr(3X) waddwstr curs_addwstr(3X) wattr_get curs_attr(3X) wbkgdset curs_bkgd(3X) wbkgrnd curs_bkgrnd(3X) wbkgrndset curs_bkgrnd(3X) wborder curs_border(3X) wborder_set curs_border_set(3X) wchgat curs_attr(3X) wclear curs_clear(3X) wclrtobot curs_clear(3X) wclrtoeol curs_clear(3X) wcolor_set curs_attr(3X) wcursyncup curs_window(3X) wdelch curs_delch(3X) wdeleteln curs_deleteln(3X) wecho_wchar curs_add_wch(3X) wechochar curs_addch(3X) wenclose curs_mouse(3X)* werase curs_clear(3X) wget_wch curs_get_wch(3X) wget_wstr curs_get_wstr(3X) wgetbkgrnd curs_bkgrnd(3X) wgetch curs_getch(3X) wgetdelay curs_opaque(3X)* wgetn_wstr curs_get_wstr(3X) wgetnstr curs_getstr(3X) wgetparent curs_opaque(3X)* wgetscrreg curs_opaque(3X)* wgetstr curs_getstr(3X) whline curs_border(3X) whline_set curs_border_set(3X) win_wch curs_in_wch(3X) win_wchnstr curs_in_wchstr(3X) win_wchstr curs_in_wchstr(3X) winch curs_inch(3X) winchnstr curs_inchstr(3X) winchstr curs_inchstr(3X) winnstr curs_instr(3X) winnwstr curs_inwstr(3X) wins_nwstr curs_ins_wstr(3X) wins_wch curs_ins_wch(3X) wins_wstr curs_ins_wstr(3X) winsch curs_insch(3X) winsdelln curs_deleteln(3X) winsertln curs_deleteln(3X) winsnstr curs_insstr(3X) winsstr curs_insstr(3X) winstr curs_instr(3X) winwstr curs_inwstr(3X) wmouse_trafo curs_mouse(3X)* wmove curs_move(3X) wnoutrefresh curs_refresh(3X) wprintw curs_printw(3X) wredrawln curs_refresh(3X) wrefresh curs_refresh(3X) wresize wresize(3X)* wscanw curs_scanw(3X) wscrl curs_scroll(3X) wsetscrreg curs_outopts(3X) wstandend curs_attr(3X) wstandout curs_attr(3X)
ncurses's screen-pointer extension adds additional functions corresponding to many of the above, each with an "_sp" suffix; see curs_sp_funcs(3X).
The availability of some extensions is configurable when ncurses is compiled; see sections "ALTERNATE CONFIGURATIONS" and "EXTENSIONS" below.
RETURN VALUE Unless otherwise noted, functions that return an integer return OK on success and ERR on failure. Functions that return pointers return NULL on failure. Typically, ncurses treats a null pointer passed as a function parameter as a failure. Functions prefixed with "mv" first perform cursor movement and fail if the position (y, x) is outside the window boundaries.
ENVIRONMENT The following symbols from the process environment customize the runtime behavior of ncurses applications. The library may be configured to disregard the variables TERMINFO, TERMINFO_DIRS, TERMPATH, and HOME, if the user is the superuser (root), or the application uses setuid(2) or setgid(2).
BAUDRATE The debugging library checks this variable when the application has redirected output to a file. Its integral value is used for the baud rate. If that value is absent or invalid, ncurses uses 9600. This feature allows testers to construct repeatable test cases that take into account optimization decisions that depend on baud rate.
CC (command character) When set, the command_character (cmdch) capability value of loaded terminfo entries changes to the value of this variable. Very few terminfo entries provide this feature.
Because this name is also used in development environments to represent the C compiler's name, ncurses ignores its value if it is not one character in length.
COLUMNS This variable specifies the width of the screen in characters. Applications running in a windowing environment usually are able to obtain the width of the window in which they are executing. If COLUMNS is not defined and the terminal's screen size is not available from the terminal driver, ncurses uses the size specified by the columns (cols) capability of the terminal type's entry in the terminfo database, if any.
It is important that your application use the correct screen size. Automatic detection thereof is not always possible because an application may be running on a host that does not honor NAWS (Negotiations About Window Size) or as a different user ID than the owner of the terminal device file. Setting COLUMNS and/or LINES overrides the library's use of the screen size obtained from the operating system.
The COLUMNS and LINES variables may be specified independently. This property is useful to circumvent misfeatures of legacy terminal type
ESCDELAY For curses to distinguish the ESC character resulting from a user's press of the "Escape" key on the input device from one beginning an escape sequence (as commonly produced by function keys), it waits after receiving the escape character to see if further characters are available on the input stream within a short interval. A global variable ESCDELAY stores this interval in milliseconds. The default value of 1000 (one second) is adequate for most uses. This environment variable overrides it.
The most common instance where you may wish to change this value is to work with a remote host over a slow communication channel. If the host running a curses application does not receive the characters of an escape sequence in a timely manner, the library can interpret them as multiple key stroke events.
xterm(1) mouse events are a form of escape sequence; therefore, if your application makes heavy use of multiple-clicking, you may wish to lengthen the default value because the delay applies to the composite multi-click event as well as the individual clicks.
Portable applications should not rely upon the presence of ESCDELAY in either form, but setting the environment variable rather than the global variable does not create problems when compiling an application.
If keypad(3X) is disabled for the curses window receiving input, a program must disambiguate escape sequences itself.
HOME ncurses may read and write auxiliary terminal descriptions in .termcap and .terminfo files in the user's home directory.
LINES This counterpart to COLUMNS specifies the height of the screen in characters. The corresponding terminfo capability and code is lines. See the description of the COLUMNS variable above.
MOUSE_BUTTONS_123 (OS/2 EMX port only) OS/2 numbers a three-button mouse inconsistently with other platforms, such that 1 is the left button, 2 the right, and 3 the middle. This variable customizes the mouse button numbering. Its value must be three digits 1-3 in any order. By default, ncurses assumes a numbering of "132".
NCURSES_ASSUMED_COLORS If set, this variable overrides the ncurses library's compiled-in assumption that the terminal's default colors are white on black; see default_colors(3X). Set the foreground and background color values with this environment variable by assigning it two integer values separated by a comma, indicating foregound and background color numbers, respectively.
For example, to tell ncurses not to assume anything about the colors, use a value of "-1,-1". To make the default color scheme green on black, use "2,0". ncurses accepts integral values from -1 up to the value of the terminfo max_colors (colors) capability.
NCURSES_CONSOLE2 NCURSES_GPM_TERMS (Linux only) When ncurses is configured to use the GPM interface, this variable may list one or more terminal names against which the TERM variable (see below) is matched. An empty value disables the GPM interface, using ncurses's built-in support for xterm(1) mouse protocols instead. If the variable is absent, ncurses attempts to open GPM if TERM contains "linux".
NCURSES_NO_HARD_TABS ncurses may use tab characters in cursor movement optimization. In some cases, your terminal driver may not handle them properly. Set this environment variable to any value to disable the feature. You can also adjust your stty(1) settings to avoid the problem.
NCURSES_NO_MAGIC_COOKIE Many terminals store video attributes as a property of a character cell, as curses does. Historically, some recorded changes in video attributes as data that logically occupies character cells on the display, switching attributes on or off, similarly to tags in a markup language; these are termed "magic cookies", and must be subsequently overprinted. If the terminfo entry for your terminal type does not adequately describe its handling of magic cookies, set this variable to any value to instruct ncurses to disable attributes entirely.
NCURSES_NO_PADDING Most terminal type descriptions in the terminfo database detail hardware devices. Many people use curses-based applications in terminal emulator programs that run in a windowing environment. These programs can duplicate all of the important features of a hardware terminal, but often lack their limitations. Chief among these absent drawbacks is the problem of data flow management; that is, limiting the speed of communication to what the hardware could handle. Unless a hardware terminal is interfaced into a terminal concentrator (which does flow control), an application must manage flow control itself to prevent overruns and data loss.
A solution that comes at no hardware cost is for an application to pause after directing a terminal to execute an operation that it performs slowly, such as clearing the display. Many terminal type descriptions, including that for the VT100, embed delay specifications in capabilities. You may wish to use these terminal descriptions without paying the performance penalty. Set NCURSES_NO_PADDING to any value to disable all but mandatory padding. Mandatory padding is used by such terminal capabilities as flash_screen (flash).
NCURSES_NO_SETBUF (Obsolete) Prior to internal changes developed in ncurses 5.9 (patches 20120825 through 20130126), the library used setbuf(3) to enable fully buffered output when initializing the terminal. This was done, as in SVr4 curses, to increase performance. For testing purposes, both of ncurses and of certain applications, this feature was made optional. Setting this variable disabled output buffering, leaving the output stream in the original (usually line-buffered) mode.
Nowadays, ncurses performs its own buffering and does not require this workaround; it does not modify the buffering of the standard output stream. This approach makes signal handling, as for interrupts, more robust. A drawback is that certain unconventional programs mixed stdio(3) calls with ncurses calls and (usually) got the behavior they
NCURSES_NO_UTF8_ACS At initialization, ncurses inspects the TERM environment variable for special cases where VT100 forms-drawing characters (and the corresponding alternate character set terminfo capabilities) are known to be unsupported by terminal types that otherwise claim VT100 compatibility. Specifically, when running in a UTF-8 locale, the Linux virtual console device and the GNU screen(1) program ignore them. Set this variable to a nonzero value to instruct ncurses that the terminal's ACS support is broken; the library then outputs Unicode code points that correspond to the forms-drawing characters. Set it to zero (or a non-integer) to disable the special check for terminal type names matching "linux" or "screen", directing ncurses to assume that the ACS feature works if the terminal type description advertises it.
As an alternative to use of this variable, ncurses checks for an extended terminfo numeric capability U8 that can be compiled using "tic -x". Examples follow.
# linux console, if patched to provide working # VT100 shift-in/shift-out, with corresponding font. linux-vt100|linux console with VT100 line-graphics, U8#0, use=linux,
# uxterm with vt100Graphics resource set to false xterm-utf8|xterm relying on UTF-8 line-graphics, U8#1, use=xterm,
The two-character name "U8" was chosen to permit its use via ncurses's termcap interface.
NCURSES_TRACE At initialization, ncurses (in its debugging configuration) checks for this variable's presence. If defined with an integral value, the library calls curses_trace(3X) with that value as the argument.
TERM The TERM variable denotes the terminal type. Each is distinct, though many are similar. It is commonly set by terminal emulators to help applications find a workable terminal description. Some choose a popular approximation such as "ansi", "vt100", or "xterm" rather than an exact fit to their capabilities. Not infrequently, an application will have problems with that approach; for example, a key stroke may not operate correctly, or produce no effect but seeming garbage characters on the screen.
Setting TERM has no effect on hardware operation; it affects the way applications communicate with the terminal. Likewise, as a general rule (xterm(1) being a rare exception), terminal emulators that allow you to specify TERM as a parameter or configuration value do not change their behavior to match that setting.
TERMCAP If ncurses is configured with termcap support, it checks for a terminal type description in termcap format if one in terminfo format is not available. Setting this variable directs ncurses to ignore the usual termcap database location, /etc/termcap; see TERMPATH below. TERMCAP should contain either a terminal description (with newlines stripped out), or a file name indicating where the information required by the TERM environment variable is stored. tree using subdirectories named by the common first letters of the terminal types named therein. This is the scheme used in System V.
o If ncurses is configured to use hashed databases, then TERMINFO may name its location, such as /usr/share/terminfo.db, rather than /usr/share/terminfo/.
The hashed database uses less disk space and is a little faster than the directory tree. However, some applications assume the existence of the directory tree, and read it directly rather than using the terminfo API.
o If ncurses is configured with termcap support, this variable may contain the location of a termcap file.
o If the value of TERMINFO begins with "hex:" or "b64:", ncurses uses the remainder of the value as a compiled terminfo description. You might produce the base64 format using infocmp(1M).
TERMINFO=$(infocmp -0 -Q2 -q) export TERMINFO
The compiled description is used only if it corresponds to the terminal type identified by TERM.
Setting TERMINFO is the simplest, but not the only, way to direct ncurses to a terminal database. The search path is as follows.
o the last terminal database to which the running ncurses application wrote, if any
o the location specified by the TERMINFO environment variable
o $HOME/.terminfo
o locations listed in the TERMINFO_DIRS environment variable
o location(s) configured and compiled into ncurses
o @TERMINFO_DIRS@
o /usr/share/misc/terminfo
TERMINFO_DIRS This variable specifies a list of locations, akin to PATH, in which ncurses searches for the terminal type descriptions described by TERMINFO above. The list items are separated by colons on Unix and semicolons on OS/2 EMX. System V terminfo lacks a corresponding feature; TERMINFO_DIRS is an ncurses extension.
TERMPATH If TERMCAP does not hold a terminal type description or file name, then ncurses checks the contents of TERMPATH, a list of locations, akin to PATH, in which it searches for termcap terminal type descriptions. The list items are separated by colons on Unix and semicolons on OS/2 EMX.
If both TERMCAP and TERMPATH are unset or invalid, ncurses searches for the files /etc/termcap, /usr/share/misc/termcap, and $HOME/.termcap, in that order. --disable-overwrite The standard include for ncurses is as noted in SYNOPSIS:
#include <curses.h>
This option is used to avoid filename conflicts when ncurses is not the main implementation of curses of the computer. If ncurses is installed disabling overwrite, it puts its headers in a subdirectory, e.g.,
#include <ncurses/curses.h>
It also omits a symbolic link which would allow you to use -lcurses to build executables.
--enable-widec The configure script renames the library and (if the --disable-overwrite option is used) puts the header files in a different subdirectory. All of the library names have a "w" appended to them, i.e., instead of
-lncurses
you link with
-lncursesw
You must also enable the wide-character features in the header file when compiling for the wide-character library to use the extended (wide-character) functions. The symbol which enables these features has changed since X/Open Curses, Issue 4:
o Originally, the wide-character feature required the symbol _XOPEN_SOURCE_EXTENDED but that was only valid for XPG4 (1996).
o Later, that was deemed conflicting with _XOPEN_SOURCE defined to 500.
o As of mid-2018, none of the features in this implementation require a _XOPEN_SOURCE feature greater than 600. However, X/Open Curses, Issue 7 (2009) recommends defining it to 700.
o Alternatively, you can enable the feature by defining NCURSES_WIDECHAR with the caveat that some other header file than curses.h may require a specific value for _XOPEN_SOURCE (or a system-specific symbol).
The curses.h header file installed for the wide-character library is designed to be compatible with the non-wide library's header. Only the size of the WINDOW structure differs; few applications require more than pointers to WINDOWs.
If the headers are installed allowing overwrite, the wide- character library's headers should be installed last, to allow applications to be built using either library from the same set of headers.
--with-pthread changes to work with this convention.
--with-shared
--with-normal
--with-debug
--with-profile The shared and normal (static) library names differ by their suffixes, e.g., libncurses.so and libncurses.a. The debug and profiling libraries add a "_g" and a "_p" to the root names respectively, e.g., libncurses_g.a and libncurses_p.a.
--with-termlib Low-level functions which do not depend upon whether the library supports wide-characters, are provided in the tinfo library.
By doing this, it is possible to share the tinfo library between wide/normal configurations as well as reduce the size of the library when only low-level functions are needed.
Those functions are described in these pages:
o curs_extend(3X) - miscellaneous curses extensions
o curs_inopts(3X) - curses input options
o curs_kernel(3X) - low-level curses routines
o curs_termattrs(3X) - curses environment query routines
o curs_termcap(3X) - curses emulation of termcap
o curs_terminfo(3X) - curses interface to terminfo database
o curs_util(3X) - miscellaneous curses utility routines
--with-trace The trace function normally resides in the debug library, but it is sometimes useful to configure this in the shared library. Configure scripts should check for the function's existence rather than assuming it is always in the debug library.
FILES /usr/share/tabset tab stop initialization database
/usr/share/misc/terminfo compiled terminal capability database
NOTES X/Open Curses permits most functions it specifies to be made available as macros as well. ncurses does so
o for functions that return values via their parameters,
o to support obsolete features,
writes screen updates to the standard error file descriptor. This was an undocumented feature of SVr3 curses.
See subsection "Header Files" below regarding symbols exposed by inclusion of curses.h.
EXTENSIONS ncurses enables an application to capture mouse events on certain terminals, including xterm(1); see curs_mouse(3X).
ncurses provides a means of responding to window resizing events, as when running in a GUI terminal emulator application such as xterm; see resizeterm(3X) and wresize(3X).
ncurses allows an application to query the terminal for the presence of a wide variety of special keys; see has_key(3X).
ncurses extends the fixed set of function key capabilities specified by X/Open Curses by allowing the application programmer to define additional key events at runtime; see define_key(3X), key_defined(3X), keybound(3X), and keyok(3X).
ncurses can exploit the capabilities of terminals implementing ISO 6429/ECMA-48 SGR 39 and SGR 49 sequences, which allow an application to reset the terminal to its original foreground and background colors. From a user's perspective, the application is able to draw colored text on a background whose color is set independently, providing better control over color contrasts. See default_colors(3X).
An ncurses application can eschew knowledge of WINDOW structure internals, instead using accessor functions such as is_scrollok(3X).
ncurses enables an application to direct application output to a printer attached to the terminal device; see curs_print(3X).
ncurses offers slk_attr(3X) as a counterpart of attr_get(3X) for soft- label key lines, and extended_slk_color(3X) as a form of slk_color(3X) that can gather color information from them when many colors are supported.
Some extensions are available only if ncurses permits modification of unctrl(3X)'s behavior; see use_legacy_coding(3X). ncurses is compiled to support them; section "ALTERNATE CONFIGURATIONS" describes how.
o Rudimentary support for multi-threaded applications may be available; see curs_threads(3X).
o Functions that ease the management of multiple screens can be exposed; see curs_sp_funcs(3X).
o To aid applications to debug their memory usage, ncurses optionally offers functions to more aggressively free memory it dynamically allocates itself; see curs_memleaks(3X).
o The library facilitates auditing and troubleshooting of its behavior; see curs_trace(3X).
o The compiler option -DUSE_GETCAP causes the library to fall back to reading /etc/termcap if the terminal setup code cannot find a
PORTABILITY X/Open Curses defines two levels of conformance, "base" and "enhanced". The latter includes several additional features, such as wide-character and color support. ncurses intends base-level conformance with X/Open Curses, and supports all features of its enhanced level except the untic utility.
Differences between X/Open Curses and ncurses are documented in the "PORTABILITY" sections of applicable man pages.
Error Checking In many cases, X/Open Curses is vague about error conditions, omitting some of the SVr4 documentation.
Unlike other implementations, ncurses checks pointer parameters, such as those to WINDOW structures, to ensure that they are not null. This is done primarily to guard against programmer error. The standard interface does not provide a way for the library to tell an application which of several possible errors occurred. Relying on this (or some other) extension adversely affects the portability of curses applications.
Padding Differences In historical curses implementations, delays embedded in the terminfo capabilities carriage_return (cr), scroll_forward (ind), cursor_left (cub1), form_feed (ff), and tab (ht) activated corresponding delay bits in the Unix terminal driver. ncurses performs all padding by sending NUL bytes to the device. This method is slightly more expensive, but narrows the interface to the Unix kernel significantly and correspondingly increases the package's portability.
Header Files The header file curses.h itself includes the header files stdio.h and unctrl.h.
X/Open Curses has more to say,
The inclusion of curses.h may make visible all symbols from the headers stdio.h, term.h, termios.h, and wchar.h.
but does not finish the story. A more complete account follows.
o Starting with 4BSD curses (1980) all implementations have provided a curses.h file.
BSD curses code included curses.h and unctrl.h from an internal header file curses.ext, where "ext" abbreviated "externs".
The implementations of printw and scanw used undocumented internal functions of the standard I/O library (_doprnt and _doscan), but nothing in curses.h itself relied upon stdio.h.
o SVr2 curses added newterm, which relies upon stdio.h because its function prototype employs the FILE type.
SVr4 curses added putwin and getwin, which also use stdio.h.
X/Open Curses specifies all three of these functions.
o X/Open Curses and SVr4 curses are inconsistent with respect to unctrl.h.
As noted in curs_util(3X), ncurses includes unctrl.h from curses.h (as SVr4 does).
o X/Open Curses's comments about term.h and termios.h may refer to HP-UX and AIX.
HP-UX curses includes term.h from curses.h to declare setupterm in curses.h, but ncurses and Solaris curses do not.
AIX curses includes term.h and termios.h. Again, ncurses and Solaris curses do not.
o X/Open Curses says that curses.h may include term.h, but does not require it to do so.
Some programs use functions declared in both curses.h and term.h, and must include both header files in the same module. Very old versions of AIX curses required inclusion of curses.h before term.h.
The header files supplied by ncurses include the standard library headers required for its declarations, so ncurses's own header files can be included in any order. But for portability, you should include curses.h before term.h.
o X/Open Curses says "may make visible" because including a header file does not necessarily make visible all of the symbols in it (consider #ifdef and similar).
For instance, ncurses's curses.h may include wchar.h if the proper symbol is defined, and if ncurses is configured for wide-character support. If wchar.h is included, its symbols may be made visible depending on the value of the _XOPEN_SOURCE feature test macro.
o X/Open Curses mandates an application's inclusion of one standard C library header in a special case: stdarg.h before curses.h to prototype the functions vw_printw and vw_scanw (as well as the obsolete vwprintw and vwscanw). Each of these takes a variadic argument list, a va_list parameter, like that of printf(3).
SVr3 curses introduced the two obsolete functions, and X/Open Curses the others. In between, SVr4 curses provided for the possibility that an application might include either varargs.h or stdarg.h. These represented contrasting approaches to handling variadic argument lists. The older interface, varargs.h, used a pointer to char for variadic functions' va_list parameter. Later, the list acquired its own standard data type, va_list, defined in stdarg.h, empowering the compiler to check the types of a function call's actual parameters against the formal ones declared in its prototype.
No conforming implementations of X/Open Curses require an application to include stdarg.h before curses.h because they either have allowed for a special type, or, like ncurses, they include stdarg.h themselves to provide a portable interface.
ncurses 6.5 2024-04-27 ncurses(3X)