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#include <curses.h>
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; term info 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.
| &#187; | 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. |
| &#187; | 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. |
| &#187; | PORTABILITY discusses matters (beyond the exercise of extensions) that should be considered when writing to a curses standard, or for multiple implementations. |
| &#187; | 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). |
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.
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).
In addition to drawing characters on the screen, rendering attributes and colors may be supported, causing the characters to show up in such modes as underlined, in reverse video, or in color on terminals that support such display enhancements. See curs_attr(3X).
curses predefines constants for a small set of forms-drawing graphics 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.
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 term info. 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.
Four functions prefixed with p require a pad argument.
In function synopses, ncurses man pages apply the following names to parameters.
| ncurses | is the library in its non-wide configuration, handling only eight-bit characters. It stores a character combined with 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.
| ||||||||||
| 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 bkgd becomes bkgrnd; the window border-drawing and -clearing functions are suffixed with _set; and character attribute manipulation functions like attron become attr_on. | |||||||||||
curses 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) derwin curs_window(3X) doupdate curs_refresh(3X) dupwin curs_window(3X) echo curs_inopts(3X) echo_wchar curs_add_wch(3X) echochar curs_addch(3X) endwin curs_initscr(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)* init_pair curs_color(3X) initscr curs_initscr(3X) innstr curs_instr(3X) innwstr curs_inwstr(3X) ins_nwstr curs_ins_wstr(3X) ins_wch curs_ins_wch(3X) ins_wstr curs_ins_wstr(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) mvget_wstr curs_get_wstr(3X) mvgetch curs_getch(3X) mvgetn_wstr curs_get_wstr(3X) mvgetnstr curs_getstr(3X) mvgetstr curs_getstr(3X) mvhline curs_border(3X) mvhline_set curs_border_set(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) mvwvline curs_border(3X) mvwvline_set curs_border_set(3X) napms curs_kernel(3X) newpad curs_pad(3X) newterm curs_initscr(3X) newwin curs_window(3X) nl curs_inopts(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) slk_refresh curs_slk(3X) slk_restore curs_slk(3X) slk_set curs_slk(3X) slk_touch curs_slk(3X) slk_wset curs_slk(3X) standend curs_attr(3X) standout curs_attr(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) wattr_off curs_attr(3X) wattr_on curs_attr(3X) wattr_set curs_attr(3X) wattroff curs_attr(3X) wattron curs_attr(3X) wattrset curs_attr(3X) wbkgd curs_bkgd(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) wsyncdown curs_window(3X) wsyncup curs_window(3X) wtimeout curs_inopts(3X) wtouchln curs_touch(3X) wunctrl curs_util(3X) wvline curs_border(3X) wvline_set curs_border_set(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.
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.
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 descriptions;
xterm(1) descriptions specifying 65 lines were once notorious.
For best results,
avoid specifying
cols and
lines capability codes in
term info descriptions of terminal emulators.
use_env(3X) can disable use of the process environment
in determining the screen size.
use_tioctl(3X) can update
COLUMNS and
LINES to match the screen size obtained from system calls or the terminal
database.
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.
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
term info max_colors (colors) capability.
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).
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 expected.
This is no longer the case;
ncurses does not write to the standard output file descriptor through a
stdio-buffered stream.
As a special case,
low-level API calls such as putp(3X) still use the
standard output stream.
High-level
curses calls such as printw(3X) do not.
As an alternative to use of this variable,
ncurses checks for an extended
term info numeric capability U8
that can be compiled using
tic -x. Examples follow.
The two-character name U8 was chosen to permit its use via
ncurses's termcap interface.
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.
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
term info database,
if any.
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.
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
term info 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.
NCURSES_CONSOLE2
(MinGW port only)
The
Console2
program defectively handles the Microsoft Console API call
Create Console Screen Buffer. Applications that use it will hang.
However,
it is possible to simulate the action of this call by mapping
coordinates,
explicitly saving and restoring the original screen contents.
Setting the environment variable
NCGDB has the same effect.
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
term info 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
term info 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.
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.
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
term info 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.
# 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,
amp;
# uxterm with vt100Graphics resource set to false
xterm-utf8|xterm relying on UTF-8 line-graphics,
U8#1, use=xterm,
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.
TERMCAP
If
ncurses is configured with
termcap support,
it checks for a terminal type description in
termcap format if one in
term info 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.
TERMINFO
ncurses can be configured to read terminal type description databases in various
locations using different formats.
This variable overrides the default location.
| &#187; | Descriptions in term info format are normally stored in a directory tree using subdirectories named by the common first letters of the terminal types named therein. This is the scheme used in System V. |
| &#187; | If ncurses is configured to use hashed databases, then TERM INFO may name its location, such as /usr/share/terminfo.db, rather than /usr/share/terminfo/. |
| &#187; | If ncurses is configured with termcap support, this variable may contain the location of a termcap file. | ||||
| &#187; |
If the value of
TERM INFO begins with hex: or b64:,
ncurses uses the remainder of the value as a compiled
term info description.
You might produce the base64 format using infocmp(1M).
| ||||
| The compiled description is used only if it corresponds to the terminal type identified by TERM. | |||||
| &#187; | the last terminal database to which the running ncurses application wrote, if any | ||||||
| &#187; | the location specified by the TERM INFO environment variable | ||||||
| &#187; | $HOME/.terminfo | ||||||
| &#187; | locations listed in the TERMINFO_DIRS environment variable | ||||||
| &#187; |
location(s) configured and compiled into
ncurses
| ||||||
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:
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.,
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
you link with
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:
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 | |||||||||||||||
| The configure script renames the library. All of the library names have a t appended to them (before any w added by --enable-widec). | |||||||||||||||
| The global variables such as LINES are replaced by macros to allow read-only access. At the same time, setter-functions are provided to set these values. Some applications (very few) may require 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:
| |||||||||||||||
| --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. | |||||||||||||||
| /usr/share/tabset | |
| tab stop initialization database | |
| /usr/share/misc/terminfo | compiled terminal capability database |
| &#187; | for functions that return values via their parameters, |
| &#187; | to support obsolete features, |
| &#187; | to reuse functions (for example, those that move the cursor before another operation), and |
| &#187; | a few special cases. |
See subsection Header Files below regarding symbols exposed by inclusion of curses.h.
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.
| &#187; | Rudimentary support for multi-threaded applications may be available; see curs_threads(3X). |
| &#187; | Functions that ease the management of multiple screens can be exposed; see curs_sp_funcs(3X). |
| &#187; | 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). |
| &#187; | The library facilitates auditing and troubleshooting of its behavior; see curs_trace(3X). |
| &#187; | The compiler option -DUSE_GETCAP causes the library to fall back to reading /etc/termcap if the terminal setup code cannot find a term info entry corresponding to TERM. Use of this feature is not recommended, as it essentially includes an entire termcap compiler in the ncurses startup code, at a cost in memory usage and application launch latency. |
Differences between X/Open Curses and ncurses are documented in the PORTABILITY sections of applicable man pages.
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.
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.
| &#187; | 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. | |
| &#187; | 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. | |
| SVr4 curses and X/Open Curses do not require the developer to include stdio.h before curses.h. Both document use of curses as requiring only curses.h. | |
| As a result, standard curses.h always includes stdio.h. | |
| &#187; | 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). | |
| &#187; | 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. | |
| &#187; | 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. | |
| &#187; | 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. | |
| &#187; | 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. | |
| 2024-04-27 | ncurses (3X) | ncurses 6.5 |
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| “ | As soon as we started programming, we found to our surprise that it wasn't as easy to get programs right as we had thought. Debugging had to be discovered. I can remember the exact instant when I realized that a large part of my life from then on was going to be spent in finding mistakes in my own programs. | ” |
| — Maurice Wilkes | ||