ncurses - CRT screen handling and optimization package
The ncurses library routines give the user a terminal-independent method of updating character screens with reasonable optimization. This implementation is "new curses" (ncurses) and is the approved replacement for 4.4BSD classic curses, which has been discontinued. This describes ncurses version 6.2 (patch 20200725). The ncurses library emulates the curses library of System V Release 4 UNIX, and XPG4 (X/Open Portability Guide) curses (also known as XSI curses). XSI stands for X/Open System Interfaces Extension. The ncurses library is freely redistributable in source form. Differences from the SVr4 curses are summarized under the EXTENSIONS and PORTABIL- ITY sections below and described in detail in the respective EXTEN- SIONS, PORTABILITY and BUGS sections of individual man pages. The ncurses library also provides many useful extensions, i.e., fea- tures which cannot be implemented by a simple add-on library but which require access to the internals of the library. A program using these routines must be linked with the -lncurses option, or (if it has been generated) with the debugging library -lncurses_g. (Your system integrator may also have installed these libraries under the names -lcurses and -lcurses_g.) The ncurses_g library generates trace logs (in a file called 'trace' in the current directory) that describe curses actions. See also the section on ALTERNATE CONFIGURATIONS. The ncurses package supports: overall screen, window and pad manipula- tion; output to windows and pads; reading terminal input; control over terminal and curses input and output options; environment query rou- tines; color manipulation; use of soft label keys; terminfo capabili- ties; and access to low-level terminal-manipulation routines.
The library uses the locale which the calling program has initialized. That is normally done with setlocale: setlocale(LC_ALL, ""); If the locale is not initialized, the library assumes that characters are printable as in ISO-8859-1, to work with certain legacy programs. You should initialize the locale and not rely on specific details of the library when the locale has not been setup. The function initscr or newterm must be called to initialize the library before any of the other routines that deal with windows and screens are used. The routine endwin(3x) must be called before exit- ing. To get character-at-a-time input without echoing (most interactive, screen oriented programs want this), the following sequence should be used: initscr(); cbreak(); noecho(); Most programs would additionally use the sequence: nonl(); intrflush(stdscr, FALSE); keypad(stdscr, TRUE); Before a curses program is run, the tab stops of the terminal should be set and its initialization strings, if defined, must be output. This can be done by executing the tput init command after the shell environ- ment variable TERM has been exported. tset(1) is usually responsible for doing this. [See terminfo(5) for further details.]
The ncurses library permits manipulation of data structures, called windows, which can be thought of as two-dimensional arrays of charac- ters representing all or part of a CRT screen. A default window called stdscr, which is the size of the terminal screen, is supplied. Others may be created with newwin. Note that curses does not handle overlapping windows, that's done by the panel(3x) library. This means that you can either use stdscr or divide the screen into tiled windows and not using stdscr at all. Mix- ing the two will result in unpredictable, and undesired, effects. Windows are referred to by variables declared as WINDOW *. These data structures are manipulated with routines described here and elsewhere in the ncurses manual pages. Among those, the most basic routines are move and addch. More general versions of these routines are included with names beginning with w, allowing the user to specify a window. The routines not beginning with w affect stdscr. After using routines to manipulate a window, refresh(3x) is called, telling curses to make the user's CRT screen look like stdscr. The characters in a window are actually of type chtype, (character and attribute data) so that other information about the character may also be stored with each character. Special windows called pads may also be manipulated. These are windows which are not constrained to the size of the screen and whose contents need not be completely displayed. See curs_pad(3x) for more informa- tion. In addition to drawing characters on the screen, video 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. Line drawing characters may be specified to be output. On input, curses is also able to translate arrow and function keys that transmit escape sequences into single val- ues. The video attributes, line drawing characters, and input values use names, defined in <curses.h>, such as A_REVERSE, ACS_HLINE, and KEY_LEFT.
If the environment variables LINES and COLUMNS are set, or if the pro- gram is executing in a window environment, line and column information in the environment will override information read by terminfo. This would affect a program running in an AT&T 630 layer, for example, where the size of a screen is changeable (see ENVIRONMENT). If the environment variable TERMINFO is defined, any program using curses checks for a local terminal definition before checking in the standard place. For example, if TERM is set to att4424, then the com- piled terminal definition is found in /usr/share/terminfo/a/att4424. (The a is copied from the first letter of att4424 to avoid creation of huge directories.) However, if TERMINFO is set to $HOME/myterms, curses first checks $HOME/myterms/a/att4424, and if that fails, it then checks /usr/share/terminfo/a/att4424. This is useful for developing experimental definitions or when write permission in /usr/share/terminfo is not available. The integer variables LINES and COLS are defined in <curses.h> and will be filled in by initscr with the size of the screen. The constants TRUE and FALSE have the values 1 and 0, respectively. The curses routines also define the WINDOW * variable curscr which is used for certain low-level operations like clearing and redrawing a screen containing garbage. The curscr can be used in only a few rou- tines.
Many curses routines have two or more versions. The routines prefixed with w require a window argument. The routines prefixed with p require a pad argument. Those without a prefix generally use stdscr. The routines prefixed with mv require a y and x coordinate to move to before performing the appropriate action. The mv routines imply a call to move before the call to the other routine. The coordinate y always refers to the row (of the window), and x always refers to the column. The upper left-hand corner is always (0,0), not (1,1). The routines prefixed with mvw take both a window argument and x and y coordinates. The window argument is always specified before the coor- dinates. In each case, win is the window affected, and pad is the pad affected; win and pad are always pointers to type WINDOW. Option setting routines require a Boolean flag bf with the value TRUE or FALSE; bf is always of type bool. Most of the data types used in the library routines, such as WINDOW, SCREEN, bool, and chtype are defined in <curses.h>. Types used for the terminfo routines such as TERMINAL are defined in <term.h>. This manual page describes functions which may appear in any configura- tion of the library. There are two common configurations of the library: ncurses the "normal" library, which handles 8-bit characters. The nor- mal (8-bit) library stores characters combined with attributes in chtype data. Attributes alone (no corresponding character) may be stored in chtype or the equivalent attr_t data. In either case, the data is stored in something like an integer. Each cell (row and column) in a WINDOW is stored as a chtype. ncursesw the so-called "wide" library, which handles multibyte charac- ters (see the section on ALTERNATE CONFIGURATIONS). The "wide" library includes all of the calls from the "normal" library. It adds about one third more calls using data types which store multibyte characters: cchar_t corresponds to chtype. However it is a structure, because more data is stored than can fit into an integer. The characters are large enough to require a full integer value - and there may be more than one character per cell. The video attributes and color are stored in separate fields of the structure. Each cell (row and column) in a WINDOW is stored as a cchar_t. The setcchar(3x) and getcchar(3x) functions store and retrieve the data from a cchar_t structure. wchar_t stores a "wide" character. Like chtype, this may be an integer. wint_t stores a wchar_t or WEOF - not the same, though both may have the same size. The "wide" library provides new functions which are analogous to functions in the "normal" library. There is a naming con- vention which relates many of the normal/wide variants: a "_w" is inserted into the name. For example, waddch becomes wadd_wch.
The following table lists the curses routines provided in the "normal" and "wide" libraries and the names of the manual pages on which they are described. Routines flagged with "*" are ncurses-specific, not described by XPG4 or present in SVr4. curses Routine Name Manual Page Name --------------------------------------------- COLOR_PAIR curs_color(3x) PAIR_NUMBER curs_attr(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_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_cleared curs_opaque(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_nodelay curs_opaque(3x)* is_notimeout curs_opaque(3x)* is_pad curs_opaque(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_outopts(3x) nocbreak curs_inopts(3x) nodelay curs_inopts(3x) noecho curs_inopts(3x) nofilter curs_util(3x)* nonl curs_outopts(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_term curs_initscr(3x) setcchar curs_getcchar(3x) setscrreg curs_outopts(3x) setsyx curs_kernel(3x) setterm curs_terminfo(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)* 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_tioctl curs_util(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) Depending on the configuration, additional sets of functions may be available: curs_memleaks(3x) - curses memory-leak checking curs_sp_funcs(3x) - curses screen-pointer extension curs_threads(3x) - curses thread support curs_trace(3x) - curses debugging routines
Routines that return an integer return ERR upon failure and an integer value other than ERR upon successful completion, unless otherwise noted in the routine descriptions. As a general rule, routines check for null pointers passed as parame- ters, and handle this as an error. All macros return the value of the w version, except setscrreg, wsetscrreg, getyx, getbegyx, and getmaxyx. The return values of setscrreg, wsetscrreg, getyx, getbegyx, and getmaxyx are undefined (i.e., these should not be used as the right-hand side of assignment statements). Functions with a "mv" prefix first perform a cursor movement using wmove, and return an error if the position is outside the window, or if the window pointer is null. Most "mv"-prefixed functions (except vari- adic functions such as mvprintw) are provided both as macros and func- tions. Routines that return pointers return NULL on error.
The following environment symbols are useful for customizing the run- time behavior of the ncurses library. The most important ones have been already discussed in detail.
When set, change occurrences of the command_character (i.e., the cmdch capability) of the loaded terminfo entries to the value of this vari- able. 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 it if it does not happen to be a single character.
The debugging library checks this environment variable when the appli- cation has redirected output to a file. The variable's numeric value is used for the baudrate. If no value is found, ncurses uses 9600. This allows testers to construct repeatable test-cases that take into account costs that depend on baudrate.
Specify 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 neither the COLUMNS value nor the terminal's screen size is available, ncurses uses the size which may be specified in the terminfo database (i.e., the cols capability). It is important that your application use a correct size for the screen. This is not always possible because your application may be running on a host which does not honor NAWS (Negotiations About Window Size), or because you are temporarily running as another user. How- ever, setting COLUMNS and/or LINES overrides the library's use of the screen size obtained from the operating system. Either COLUMNS or LINES symbols may be specified independently. This is mainly useful to circumvent legacy misfeatures of terminal descrip- tions, e.g., xterm which commonly specifies a 65 line screen. For best results, lines and cols should not be specified in a terminal descrip- tion for terminals which are run as emulations. Use the use_env function to disable all use of external environment (but not including system calls) to determine the screen size. Use the use_tioctl function to update COLUMNS or LINES to match the screen size obtained from system calls or the terminal database.
Specifies the total time, in milliseconds, for which ncurses will await a character sequence, e.g., a function key. The default value, 1000 milliseconds, is enough for most uses. However, it is made a variable to accommodate unusual applications. The most common instance where you may wish to change this value is to work with slow hosts, e.g., running on a network. If the host cannot read characters rapidly enough, it will have the same effect as if the terminal did not send characters rapidly enough. The library will still see a timeout. Note that xterm mouse events are built up from character sequences received from the xterm. If your application makes heavy use of multi- ple-clicking, you may wish to lengthen this default value because the timeout applies to the composed multi-click event as well as the indi- vidual clicks. In addition to the environment variable, this implementation provides a global variable with the same name. 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.
Tells ncurses where your home directory is. That is where it may read and write auxiliary terminal descriptions: $HOME/.termcap $HOME/.terminfo
Like COLUMNS, specify the height of the screen in characters. See COL- UMNS for a detailed description.
This applies only to the OS/2 EMX port. It specifies the order of but- tons on the mouse. OS/2 numbers a 3-button mouse inconsistently from other platforms: 1 = left 2 = right 3 = middle. This variable lets you customize the mouse. The variable must be three numeric digits 1-3 in any order, e.g., 123 or 321. If it is not speci- fied, ncurses uses 132.
Override the compiled-in assumption that the terminal's default colors are white-on-black (see default_colors(3x)). You may set the fore- ground and background color values with this environment variable by proving a 2-element list: foreground,background. For example, to tell ncurses to not assume anything about the colors, set this to "-1,-1". To make it green-on-black, set it to "2,0". Any positive value from zero to the terminfo max_colors value is allowed.
This applies only to the MinGW port of ncurses. The Console2 program's handling of the Microsoft Console API call Cre- ateConsoleScreenBuffer is defective. Applications which use this 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.
This applies only to ncurses configured to use the GPM interface. If present, the environment variable is a list of one or more terminal names against which the TERM environment variable is matched. Setting it to an empty value disables the GPM interface; using the built-in support for xterm, etc. If the environment variable is absent, ncurses will attempt to open GPM if TERM contains "linux".
Ncurses may use tabs as part of the cursor movement optimization. In some cases, your terminal driver may not handle these properly. Set this environment variable to disable the feature. You can also adjust your stty settings to avoid the problem.
Some terminals use a magic-cookie feature which requires special han- dling to make highlighting and other video attributes display properly. You can suppress the highlighting entirely for these terminals by set- ting this environment variable.
Most of the terminal descriptions in the terminfo database are written for real "hardware" terminals. Many people use terminal emulators which run in a windowing environment and use curses-based applications. Terminal emulators can duplicate all of the important aspects of a hardware terminal, but they do not have the same limitations. The chief limitation of a hardware terminal from the standpoint of your application is the management of dataflow, i.e., timing. Unless a hardware terminal is interfaced into a terminal concentrator (which does flow control), it (or your application) must manage dataflow, pre- venting overruns. The cheapest solution (no hardware cost) is for your program to do this by pausing after operations that the terminal does slowly, such as clearing the display. As a result, many terminal descriptions (including the vt100) have delay times embedded. You may wish to use these descriptions, but not want to pay the performance penalty. Set the NCURSES_NO_PADDING environment variable to disable all but mandatory padding. Mandatory padding is used as a part of special con- trol sequences such as flash.
This setting is obsolete. Before changes o started with 5.9 patch 20120825 and o continued though 5.9 patch 20130126 ncurses enabled buffered output during terminal initialization. This was done (as in SVr4 curses) for performance reasons. For testing pur- poses, both of ncurses and certain applications, this feature was made optional. Setting the NCURSES_NO_SETBUF variable disabled output buffering, leaving the output in the original (usually line buffered) mode. In the current implementation, ncurses performs its own buffering and does not require this workaround. It does not modify the buffering of the standard output. The reason for the change was to make the behavior for interrupts and other signals more robust. One drawback is that certain nonconven- tional programs would mix ordinary stdio calls with ncurses calls and (usually) work. This is no longer possible since ncurses is not using the buffered standard output but its own output (to the same file descriptor). As a special case, the low-level calls such as putp still use the standard output. But high-level curses calls do not.
During initialization, the ncurses library checks for special cases where VT100 line-drawing (and the corresponding alternate character set capabilities) described in the terminfo are known to be missing. Specifically, when running in a UTF-8 locale, the Linux console emula- tor and the GNU screen program ignore these. Ncurses checks the TERM environment variable for these. For other special cases, you should set this environment variable. Doing this tells ncurses to use Unicode values which correspond to the VT100 line-drawing glyphs. That works for the special cases cited, and is likely to work for terminal emula- tors. When setting this variable, you should set it to a nonzero value. Set- ting it to zero (or to a nonnumber) disables the special check for "linux" and "screen". As an alternative to the environment variable, ncurses checks for an extended terminfo capability U8. This is a numeric capability which can be compiled using tic -x. For example # 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 name "U8" is chosen to be two characters, to permit it to be used by applications that use ncurses' termcap interface.
During initialization, the ncurses debugging library checks the NCURSES_TRACE environment variable. If it is defined, to a numeric value, ncurses calls the trace function, using that value as the argu- ment. The argument values, which are defined in curses.h, provide several types of information. When running with traces enabled, your applica- tion will write the file trace to the current directory. See curs_trace(3x) for more information.
Denotes your terminal type. Each terminal type is distinct, though many are similar. TERM is commonly set by terminal emulators to help applications find a workable terminal description. Some of those choose a popular approxi- mation, e.g., "ansi", "vt100", "xterm" rather than an exact fit. Not infrequently, your application will have problems with that approach, e.g., incorrect function-key definitions. If you set TERM in your environment, it has no effect on the operation of the terminal emulator. It only affects the way applications work within the terminal. Likewise, as a general rule (xterm being a rare exception), terminal emulators which allow you to specify TERM as a parameter or configuration value do not change their behavior to match that setting.
If the ncurses library has been configured with termcap support, ncurses will check for a terminal's description in termcap form if it is not available in the terminfo database. The TERMCAP environment variable contains either a terminal description (with newlines stripped out), or a file name telling where the informa- tion denoted by the TERM environment variable exists. In either case, setting it directs ncurses to ignore the usual place for this informa- tion, e.g., /etc/termcap.
ncurses can be configured to read from multiple terminal databases. The TERMINFO variable overrides the location for the default terminal database. Terminal descriptions (in terminal format) are stored in terminal databases: o Normally these are stored in a directory tree, using subdirectories named by the first letter of the terminal names therein. This is the scheme used in System V, which legacy Unix systems use, and the TERMINFO variable is used by curses applications on those systems to override the default location of the terminal database. o If ncurses is built to use hashed databases, then each entry in this list may be the path of a hashed database file, e.g., /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, reading it directly rather than using the terminfo library calls. o If ncurses is built with a support for reading termcap files directly, then an entry in this list may be the path of a termcap file. o If the TERMINFO variable begins with "hex:" or "b64:", ncurses uses the remainder of that variable as a compiled terminal description. You might produce the base64 format using infocmp(1m): TERMINFO="$(infocmp -0 -Q2 -q)" export TERMINFO The compiled description is used if it corresponds to the terminal identified by the TERM variable. Setting TERMINFO is the simplest, but not the only way to set location of the default terminal database. The complete list of database loca- tions in order follows: o the last terminal database to which ncurses wrote, if any, is searched first o the location specified by the TERMINFO environment variable o $HOME/.terminfo o locations listed in the TERMINFO_DIRS environment variable o one or more locations whose names are configured and compiled into the ncurses library, i.e., o /usr/local/ncurses/share/terminfo:/usr/share/terminfo (corre- sponding to the TERMINFO_DIRS variable) o /usr/share/terminfo (corresponding to the TERMINFO variable)
Specifies a list of locations to search for terminal descriptions. Each location in the list is a terminal database as described in the section on the TERMINFO variable. The list is separated by colons (i.e., ":") on Unix, semicolons on OS/2 EMX. There is no corresponding feature in System V terminfo; it is an exten- sion developed for ncurses.
If TERMCAP does not hold a file name then ncurses checks the TERMPATH environment variable. This is a list of filenames separated by spaces or colons (i.e., ":") on Unix, semicolons on OS/2 EMX. If the TERMPATH environment variable is not set, ncurses looks in the files /etc/termcap, /usr/share/misc/termcap and $HOME/.termcap, in that order. The library may be configured to disregard the following variables when the current user is the superuser (root), or if the application uses setuid or setgid permissions: $TERMINFO, $TERMINFO_DIRS, $TERMPATH, as well as $HOME.
Several different configurations are possible, depending on the config- ure script options used when building ncurses. There are a few main options whose effects are visible to the applications developer using ncurses: --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 subdi- rectory, 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 --dis- able-overwrite option is used) puts the header files in a differ- ent 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 XSI 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 file which is installed for the wide-character library is designed to be compatible with the normal library's header. Only the size of the WINDOW structure differs, and very few applications require more than a pointer to WINDOWs. If the headers are installed allowing overwrite, the wide-charac- ter library's headers should be installed last, to allow applica- tions to be built using either library from the same set of head- ers. --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 suf- fixes, e.g., libncurses.so and libncurses.a. The debug and pro- filing libraries add a "_g" and a "_p" to the root names respec- tively, e.g., libncurses_g.a and libncurses_p.a. --with-trace The trace function normally resides in the debug library, but it is sometimes useful to configure this in the shared library. Con- figure scripts should check for the function's existence rather than assuming it is always in the debug library.
/usr/share/tabset directory containing initialization files for the terminal capa- bility database /usr/share/terminfo terminal capability database
terminfo(5) and related pages whose names begin "curs_" for detailed routine descriptions. curs_variables(3x) user_caps(5) for user-defined capabilities
The ncurses library can be compiled with an option (-DUSE_GETCAP) that falls back to the old-style /etc/termcap file if the terminal setup code cannot find a terminfo entry corresponding to TERM. Use of this feature is not recommended, as it essentially includes an entire term- cap compiler in the ncurses startup code, at significant cost in core and startup cycles. The ncurses library includes facilities for capturing mouse events on certain terminals (including xterm). See the curs_mouse(3x) manual page for details. The ncurses library includes facilities for responding to window resiz- ing events, e.g., when running in an xterm. See the resizeterm(3x) and wresize(3x) manual pages for details. In addition, the library may be configured with a SIGWINCH handler. The ncurses library extends the fixed set of function key capabilities of terminals by allowing the application designer to define additional key sequences at runtime. See the define_key(3x) key_defined(3x), and keyok(3x) manual pages for details. The ncurses library can exploit the capabilities of terminals which implement the ISO-6429 SGR 39 and SGR 49 controls, which allow an application to reset the terminal to its original foreground and back- ground colors. From the users' perspective, the application is able to draw colored text on a background whose color is set independently, providing better control over color contrasts. See the default_col- ors(3x) manual page for details. The ncurses library includes a function for directing application out- put to a printer attached to the terminal device. See the curs_print(3x) manual page for details.
The ncurses library is intended to be BASE-level conformant with XSI Curses. The EXTENDED XSI Curses functionality (including color sup- port) is supported. A small number of local differences (that is, individual differences between the XSI Curses and ncurses calls) are described in PORTABILITY sections of the library man pages.
In many cases, X/Open Curses is vague about error conditions, omitting some of the SVr4 documentation. Unlike other implementations, this one checks parameters such as point- ers to WINDOW structures to ensure they are not null. The main reason for providing this behavior is 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 were detected. Relying on this (or some other) extension will adversely affect the portability of curses applications.
Most of the extensions provided by ncurses have not been standardized. Some have been incorporated into other implementations, such as PDCurses or NetBSD curses. Here are a few to consider: o The routine has_key is not part of XPG4, nor is it present in SVr4. See the curs_getch(3x) manual page for details. o The routine slk_attr is not part of XPG4, nor is it present in SVr4. See the curs_slk(3x) manual page for details. o The routines getmouse, mousemask, ungetmouse, mouseinterval, and wenclose relating to mouse interfacing are not part of XPG4, nor are they present in SVr4. See the curs_mouse(3x) manual page for details. o The routine mcprint was not present in any previous curses imple- mentation. See the curs_print(3x) manual page for details. o The routine wresize is not part of XPG4, nor is it present in SVr4. See the wresize(3x) manual page for details. o The WINDOW structure's internal details can be hidden from applica- tion programs. See curs_opaque(3x) for the discussion of is_scrol- lok, etc. o This implementation can be configured to provide rudimentary sup- port for multi-threaded applications. See curs_threads(3x) for details. o This implementation can also be configured to provide a set of functions which improve the ability to manage multiple screens. See curs_sp_funcs(3x) for details.
In historic curses versions, delays embedded in the capabilities cr, ind, cub1, ff and tab activated corresponding delay bits in the UNIX tty driver. In this implementation, all padding is done by sending NUL bytes. This method is slightly more expensive, but narrows the inter- face to the UNIX kernel significantly and increases the package's portability correspondingly.
The header file <curses.h> automatically includes the header files <stdio.h> and <unctrl.h>. X/Open Curses has more to say, but does not finish the story: The inclusion of <curses.h> may make visible all symbols from the headers <stdio.h>, <term.h>, <termios.h>, and <wchar.h>. Here is a more complete story: o Starting with BSD curses, all implementations have included <stdio.h>. BSD curses included <curses.h> and <unctrl.h> from an internal header "curses.ext" ("ext" was a short name for externs). BSD curses used <stdio.h> internally (for printw and scanw), but nothing in <curses.h> itself relied upon <stdio.h>. o SVr2 curses added newterm(3x), which relies upon <stdio.h>. That is, the function prototype uses FILE. SVr4 curses added putwin and getwin, which also use <stdio.h>. X/Open Curses documents all three of these functions. SVr4 curses and X/Open Curses do not require the developer to include <stdio.h> before including <curses.h>. Both document curses showing <curses.h> as the only required header. As a result, standard <curses.h> will always include <stdio.h>. o X/Open Curses is inconsistent with respect to SVr4 regarding <unc- trl.h>. As noted in curs_util(3x), ncurses includes <unctrl.h> from <curses.h> (like SVr4). o X/Open'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 says that <curses.h> may include <term.h>, but there is no requirement that it do that. Some programs use functions declared in both <curses.h> and <term.h>, and must include both headers in the same module. Very old versions of AIX curses required including <curses.h> before including <term.h>. Because ncurses header files include the headers needed to define datatypes used in the headers, ncurses 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 all symbols in it visible (there are ifdef's to consider). For instance, in ncurses <wchar.h> may be included if the proper symbol is defined, and if ncurses is configured for wide-character support. If the header is included, its symbols may be made visi- ble. That depends on the value used for _XOPEN_SOURCE feature test macro. o X/Open Curses documents one required header, in a special case: <stdarg.h> before <curses.h> to prototype the vw_printw and vw_scanw functions (as well as the obsolete the vwprintw and vws- canw functions). Each of those uses a va_list parameter. The two obsolete functions were introduced in SVr3. The other functions were introduced in X/Open Curses. In between, SVr4 curses provided for the possibility that an application might include either <varargs.h> or <stdarg.h>. Initially, that was done by using void* for the va_list parameter. Later, a special type (defined in <stdio.h>) was introduced, to allow for compiler type- checking. That special type is always available, because <stdio.h> is always included by <curses.h>. None of the X/Open Curses implementations require an application to include <stdarg.h> before <curses.h> because they either have allowed for a special type, or (like ncurses) include <stdarg.h> directly to provide a portable interface.
If standard output from a ncurses program is re-directed to something which is not a tty, screen updates will be directed to standard error. This was an undocumented feature of AT&T System V Release 3 curses.
Zeyd M. Ben-Halim, Eric S. Raymond, Thomas E. Dickey. Based on pcurses by Pavel Curtis. ncurses(3x)