ncurses - CRT screen handling and optimization package


   #include <curses.h>


   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 6.0 (patch 20160625).

   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
   PORTABILITY sections below and described in detail  in  the  respective
   EXTENSIONS, PORTABILITY and BUGS sections of individual man pages.

   The  ncurses  library  also  provides  many  useful  extensions,  i.e.,
   features 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

   The   ncurses   package   supports:  overall  screen,  window  and  pad
   manipulation; output to  windows  and  pads;  reading  terminal  input;
   control  over terminal and curses input and output options; environment
   query routines; color manipulation; use of soft  label  keys;  terminfo
   capabilities; 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 must be called before exiting.

   To  get  character-at-a-time  input  without echoing (most interactive,
   screen oriented programs want this), the following sequence  should  be

         initscr(); cbreak(); noecho();

   Most programs would additionally use the sequence:

         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
   environment 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
   characters  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(3CURSES) library.  This means that you can either use  stdscr
   or  divide  the  screen into tiled windows and not using stdscr at all.
   Mixing 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 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  pad(3NCURSES)  for  more

   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
   values.  The video  attributes,  line  drawing  characters,  and  input
   values  use names, defined in <curses.h>, such as A_REVERSE, ACS_HLINE,
   and KEY_LEFT.

   Environment variables
   If the environment variables LINES and  COLUMNS  are  set,  or  if  the
   program   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

   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
   compiled terminal definition is found in


   (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


   and if that fails, it then checks


   This is useful for developing experimental definitions  or  when  write
   permission in /etc/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

   Routine and Argument Names
   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

   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
   configuration of the library.  There are two common  configurations  of
   the library:

           the  "normal"  library,  which  handles  8-bit characters.  The
           normal  (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.

           the   so-called   "wide"   library,   which  handles  multibyte
           characters (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:

                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

                stores  a  "wide"  character.  Like chtype, this may be an

                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
           convention  which  relates  many of the normal/wide variants: a
           "_w" is inserted into the name.  For  example,  waddch  becomes

   Routine Name Index
   The  following  table  lists  each  curses  routine and the name of the
   manual page on which it is described.  Routines flagged  with  `*'  are
   ncurses-specific, not described by XPG4 or present in SVr4.

              curses Routine Name     Manual Page Name
              COLOR_PAIR              color(3NCURSES)
              PAIR_NUMBER             attr(3NCURSES)
              _nc_free_and_exit       memleaks(3NCURSES)*
              _nc_freeall             memleaks(3NCURSES)*
              _nc_tracebits           trace(3NCURSES)*
              _traceattr              trace(3NCURSES)*
              _traceattr2             trace(3NCURSES)*
              _tracechar              trace(3NCURSES)*
              _tracechtype            trace(3NCURSES)*
              _tracechtype2           trace(3NCURSES)*
              _tracedump              trace(3NCURSES)*
              _tracef                 trace(3NCURSES)*
              _tracemouse             trace(3NCURSES)*
              add_wch                 add_wch(3NCURSES)
              add_wchnstr             add_wchstr(3NCURSES)
              add_wchstr              add_wchstr(3NCURSES)
              addch                   addch(3NCURSES)
              addchnstr               addchstr(3NCURSES)
              addchstr                addchstr(3NCURSES)
              addnstr                 addstr(3NCURSES)
              addnwstr                addwstr(3NCURSES)
              addstr                  addstr(3NCURSES)
              addwstr                 addwstr(3NCURSES)
              assume_default_colors   default_colors(3NCURSES)*
              attr_get                attr(3NCURSES)
              attr_off                attr(3NCURSES)
              attr_on                 attr(3NCURSES)
              attr_set                attr(3NCURSES)
              attroff                 attr(3NCURSES)
              attron                  attr(3NCURSES)
              attrset                 attr(3NCURSES)
              baudrate                termattrs(3NCURSES)

              beep                    beep(3NCURSES)
              bkgd                    bkgd(3NCURSES)
              bkgdset                 bkgd(3NCURSES)
              bkgrnd                  bkgrnd(3NCURSES)
              bkgrndset               bkgrnd(3NCURSES)
              border                  border(3NCURSES)
              border_set              border_set(3NCURSES)
              box                     border(3NCURSES)
              box_set                 border_set(3NCURSES)
              can_change_color        color(3NCURSES)
              cbreak                  inopts(3NCURSES)
              chgat                   attr(3NCURSES)
              clear                   clear(3NCURSES)
              clearok                 outopts(3NCURSES)
              clrtobot                clear(3NCURSES)
              clrtoeol                clear(3NCURSES)
              color_content           color(3NCURSES)
              color_set               attr(3NCURSES)
              copywin                 overlay(3NCURSES)
              curs_set                kernel(3NCURSES)
              curses_version          extensions(3NCURSES)*
              def_prog_mode           kernel(3NCURSES)
              def_shell_mode          kernel(3NCURSES)
              define_key              define_key(3NCURSES)*
              del_curterm             terminfo(3NCURSES)
              delay_output            util(3NCURSES)
              delch                   delch(3NCURSES)
              deleteln                deleteln(3NCURSES)
              delscreen               initscr(3NCURSES)
              delwin                  window(3NCURSES)
              derwin                  window(3NCURSES)
              doupdate                refresh(3NCURSES)
              dupwin                  window(3NCURSES)
              echo                    inopts(3NCURSES)
              echo_wchar              add_wch(3NCURSES)
              echochar                addch(3NCURSES)
              endwin                  initscr(3NCURSES)
              erase                   clear(3NCURSES)
              erasechar               termattrs(3NCURSES)
              erasewchar              termattrs(3NCURSES)
              filter                  util(3NCURSES)
              flash                   beep(3NCURSES)
              flushinp                util(3NCURSES)
              get_wch                 get_wch(3NCURSES)
              get_wstr                get_wstr(3NCURSES)
              getattrs                attr(3NCURSES)
              getbegx                 legacy(3NCURSES)*
              getbegy                 legacy(3NCURSES)*
              getbegyx                getyx(3NCURSES)
              getbkgd                 bkgd(3NCURSES)
              getbkgrnd               bkgrnd(3NCURSES)
              getcchar                getcchar(3NCURSES)
              getch                   getch(3NCURSES)
              getcurx                 legacy(3NCURSES)*
              getcury                 legacy(3NCURSES)*
              getmaxx                 legacy(3NCURSES)*
              getmaxy                 legacy(3NCURSES)*
              getmaxyx                getyx(3NCURSES)
              getmouse                mouse(3NCURSES)*
              getn_wstr               get_wstr(3NCURSES)
              getnstr                 getstr(3NCURSES)
              getparx                 legacy(3NCURSES)*
              getpary                 legacy(3NCURSES)*
              getparyx                getyx(3NCURSES)
              getstr                  getstr(3NCURSES)

              getsyx                  kernel(3NCURSES)
              getwin                  util(3NCURSES)
              getyx                   getyx(3NCURSES)
              halfdelay               inopts(3NCURSES)
              has_colors              color(3NCURSES)
              has_ic                  termattrs(3NCURSES)
              has_il                  termattrs(3NCURSES)
              has_key                 getch(3NCURSES)*
              hline                   border(3NCURSES)
              hline_set               border_set(3NCURSES)
              idcok                   outopts(3NCURSES)
              idlok                   outopts(3NCURSES)
              immedok                 outopts(3NCURSES)
              in_wch                  in_wch(3NCURSES)
              in_wchnstr              in_wchstr(3NCURSES)
              in_wchstr               in_wchstr(3NCURSES)
              inch                    inch(3NCURSES)
              inchnstr                inchstr(3NCURSES)
              inchstr                 inchstr(3NCURSES)
              init_color              color(3NCURSES)
              init_pair               color(3NCURSES)
              initscr                 initscr(3NCURSES)
              innstr                  instr(3NCURSES)
              innwstr                 inwstr(3NCURSES)
              ins_nwstr               ins_wstr(3NCURSES)
              ins_wch                 ins_wch(3NCURSES)
              ins_wstr                ins_wstr(3NCURSES)
              insch                   insch(3NCURSES)
              insdelln                deleteln(3NCURSES)
              insertln                deleteln(3NCURSES)
              insnstr                 insstr(3NCURSES)
              insstr                  insstr(3NCURSES)
              instr                   instr(3NCURSES)
              intrflush               inopts(3NCURSES)
              inwstr                  inwstr(3NCURSES)
              is_cleared              opaque(3NCURSES)*
              is_idcok                opaque(3NCURSES)*
              is_idlok                opaque(3NCURSES)*
              is_immedok              opaque(3NCURSES)*
              is_keypad               opaque(3NCURSES)*
              is_leaveok              opaque(3NCURSES)*
              is_linetouched          touch(3NCURSES)
              is_nodelay              opaque(3NCURSES)*
              is_notimeout            opaque(3NCURSES)*
              is_pad                  opaque(3NCURSES)*
              is_scrollok             opaque(3NCURSES)*
              is_subwin               opaque(3NCURSES)*
              is_syncok               opaque(3NCURSES)*
              is_term_resized         resizeterm(3NCURSES)*
              is_wintouched           touch(3NCURSES)
              isendwin                initscr(3NCURSES)
              key_defined             key_defined(3NCURSES)*
              key_name                util(3NCURSES)
              keybound                keybound(3NCURSES)*
              keyname                 util(3NCURSES)
              keyok                   keyok(3NCURSES)*
              keypad                  inopts(3NCURSES)
              killchar                termattrs(3NCURSES)
              killwchar               termattrs(3NCURSES)
              leaveok                 outopts(3NCURSES)
              longname                termattrs(3NCURSES)
              mcprint                 print(3NCURSES)*
              meta                    inopts(3NCURSES)
              mouse_trafo             mouse(3NCURSES)*
              mouseinterval           mouse(3NCURSES)*

              mousemask               mouse(3NCURSES)*
              move                    move(3NCURSES)
              mvadd_wch               add_wch(3NCURSES)
              mvadd_wchnstr           add_wchstr(3NCURSES)
              mvadd_wchstr            add_wchstr(3NCURSES)
              mvaddch                 addch(3NCURSES)
              mvaddchnstr             addchstr(3NCURSES)
              mvaddchstr              addchstr(3NCURSES)
              mvaddnstr               addstr(3NCURSES)
              mvaddnwstr              addwstr(3NCURSES)
              mvaddstr                addstr(3NCURSES)
              mvaddwstr               addwstr(3NCURSES)
              mvchgat                 attr(3NCURSES)
              mvcur                   terminfo(3NCURSES)
              mvdelch                 delch(3NCURSES)
              mvderwin                window(3NCURSES)
              mvget_wch               get_wch(3NCURSES)
              mvget_wstr              get_wstr(3NCURSES)
              mvgetch                 getch(3NCURSES)
              mvgetn_wstr             get_wstr(3NCURSES)
              mvgetnstr               getstr(3NCURSES)
              mvgetstr                getstr(3NCURSES)
              mvhline                 border(3NCURSES)
              mvhline_set             border_set(3NCURSES)
              mvin_wch                in_wch(3NCURSES)
              mvin_wchnstr            in_wchstr(3NCURSES)
              mvin_wchstr             in_wchstr(3NCURSES)
              mvinch                  inch(3NCURSES)
              mvinchnstr              inchstr(3NCURSES)
              mvinchstr               inchstr(3NCURSES)
              mvinnstr                instr(3NCURSES)
              mvinnwstr               inwstr(3NCURSES)
              mvins_nwstr             ins_wstr(3NCURSES)
              mvins_wch               ins_wch(3NCURSES)
              mvins_wstr              ins_wstr(3NCURSES)
              mvinsch                 insch(3NCURSES)
              mvinsnstr               insstr(3NCURSES)
              mvinsstr                insstr(3NCURSES)
              mvinstr                 instr(3NCURSES)
              mvinwstr                inwstr(3NCURSES)
              mvprintw                printw(3NCURSES)
              mvscanw                 scanw(3NCURSES)
              mvvline                 border(3NCURSES)
              mvvline_set             border_set(3NCURSES)
              mvwadd_wch              add_wch(3NCURSES)
              mvwadd_wchnstr          add_wchstr(3NCURSES)
              mvwadd_wchstr           add_wchstr(3NCURSES)
              mvwaddch                addch(3NCURSES)
              mvwaddchnstr            addchstr(3NCURSES)
              mvwaddchstr             addchstr(3NCURSES)
              mvwaddnstr              addstr(3NCURSES)
              mvwaddnwstr             addwstr(3NCURSES)
              mvwaddstr               addstr(3NCURSES)
              mvwaddwstr              addwstr(3NCURSES)
              mvwchgat                attr(3NCURSES)
              mvwdelch                delch(3NCURSES)
              mvwget_wch              get_wch(3NCURSES)
              mvwget_wstr             get_wstr(3NCURSES)
              mvwgetch                getch(3NCURSES)
              mvwgetn_wstr            get_wstr(3NCURSES)
              mvwgetnstr              getstr(3NCURSES)
              mvwgetstr               getstr(3NCURSES)
              mvwhline                border(3NCURSES)
              mvwhline_set            border_set(3NCURSES)
              mvwin                   window(3NCURSES)

              mvwin_wch               in_wch(3NCURSES)
              mvwin_wchnstr           in_wchstr(3NCURSES)
              mvwin_wchstr            in_wchstr(3NCURSES)
              mvwinch                 inch(3NCURSES)
              mvwinchnstr             inchstr(3NCURSES)
              mvwinchstr              inchstr(3NCURSES)
              mvwinnstr               instr(3NCURSES)
              mvwinnwstr              inwstr(3NCURSES)
              mvwins_nwstr            ins_wstr(3NCURSES)
              mvwins_wch              ins_wch(3NCURSES)
              mvwins_wstr             ins_wstr(3NCURSES)
              mvwinsch                insch(3NCURSES)
              mvwinsnstr              insstr(3NCURSES)
              mvwinsstr               insstr(3NCURSES)
              mvwinstr                instr(3NCURSES)
              mvwinwstr               inwstr(3NCURSES)
              mvwprintw               printw(3NCURSES)
              mvwscanw                scanw(3NCURSES)
              mvwvline                border(3NCURSES)
              mvwvline_set            border_set(3NCURSES)
              napms                   kernel(3NCURSES)
              newpad                  pad(3NCURSES)
              newterm                 initscr(3NCURSES)
              newwin                  window(3NCURSES)
              nl                      outopts(3NCURSES)
              nocbreak                inopts(3NCURSES)
              nodelay                 inopts(3NCURSES)
              noecho                  inopts(3NCURSES)
              nofilter                util(3NCURSES)*
              nonl                    outopts(3NCURSES)
              noqiflush               inopts(3NCURSES)
              noraw                   inopts(3NCURSES)
              notimeout               inopts(3NCURSES)
              overlay                 overlay(3NCURSES)
              overwrite               overlay(3NCURSES)
              pair_content            color(3NCURSES)
              pechochar               pad(3NCURSES)
              pnoutrefresh            pad(3NCURSES)
              prefresh                pad(3NCURSES)
              printw                  printw(3NCURSES)
              putp                    terminfo(3NCURSES)
              putwin                  util(3NCURSES)
              qiflush                 inopts(3NCURSES)
              raw                     inopts(3NCURSES)
              redrawwin               refresh(3NCURSES)
              refresh                 refresh(3NCURSES)
              reset_prog_mode         kernel(3NCURSES)
              reset_shell_mode        kernel(3NCURSES)
              resetty                 kernel(3NCURSES)
              resize_term             resizeterm(3NCURSES)*
              resizeterm              resizeterm(3NCURSES)*
              restartterm             terminfo(3NCURSES)
              ripoffline              kernel(3NCURSES)
              savetty                 kernel(3NCURSES)
              scanw                   scanw(3NCURSES)
              scr_dump                scr_dump(3NCURSES)
              scr_init                scr_dump(3NCURSES)
              scr_restore             scr_dump(3NCURSES)
              scr_set                 scr_dump(3NCURSES)
              scrl                    scroll(3NCURSES)
              scroll                  scroll(3NCURSES)
              scrollok                outopts(3NCURSES)
              set_curterm             terminfo(3NCURSES)
              set_term                initscr(3NCURSES)
              setcchar                getcchar(3NCURSES)

              setscrreg               outopts(3NCURSES)
              setsyx                  kernel(3NCURSES)
              setterm                 terminfo(3NCURSES)
              setupterm               terminfo(3NCURSES)
              slk_attr                slk(3NCURSES)*
              slk_attr_off            slk(3NCURSES)
              slk_attr_on             slk(3NCURSES)
              slk_attr_set            slk(3NCURSES)
              slk_attroff             slk(3NCURSES)
              slk_attron              slk(3NCURSES)
              slk_attrset             slk(3NCURSES)
              slk_clear               slk(3NCURSES)
              slk_color               slk(3NCURSES)
              slk_init                slk(3NCURSES)
              slk_label               slk(3NCURSES)
              slk_noutrefresh         slk(3NCURSES)
              slk_refresh             slk(3NCURSES)
              slk_restore             slk(3NCURSES)
              slk_set                 slk(3NCURSES)
              slk_touch               slk(3NCURSES)
              standend                attr(3NCURSES)
              standout                attr(3NCURSES)
              start_color             color(3NCURSES)
              subpad                  pad(3NCURSES)
              subwin                  window(3NCURSES)
              syncok                  window(3NCURSES)
              term_attrs              termattrs(3NCURSES)
              termattrs               termattrs(3NCURSES)
              termname                termattrs(3NCURSES)
              tgetent                 termcap(3NCURSES)
              tgetflag                termcap(3NCURSES)
              tgetnum                 termcap(3NCURSES)
              tgetstr                 termcap(3NCURSES)
              tgoto                   termcap(3NCURSES)
              tigetflag               terminfo(3NCURSES)
              tigetnum                terminfo(3NCURSES)
              tigetstr                terminfo(3NCURSES)
              tiparm                  terminfo(3NCURSES)*
              timeout                 inopts(3NCURSES)
              touchline               touch(3NCURSES)
              touchwin                touch(3NCURSES)
              tparm                   terminfo(3NCURSES)
              tputs                   termcap(3NCURSES)
              tputs                   terminfo(3NCURSES)
              trace                   trace(3NCURSES)*
              typeahead               inopts(3NCURSES)
              unctrl                  util(3NCURSES)
              unget_wch               get_wch(3NCURSES)
              ungetch                 getch(3NCURSES)
              ungetmouse              mouse(3NCURSES)*
              untouchwin              touch(3NCURSES)
              use_default_colors      default_colors(3NCURSES)*
              use_env                 util(3NCURSES)
              use_extended_names      extensions(3NCURSES)*
              use_legacy_coding       legacy_coding(3NCURSES)*
              use_tioctl              util(3NCURSES)
              vid_attr                terminfo(3NCURSES)
              vid_puts                terminfo(3NCURSES)
              vidattr                 terminfo(3NCURSES)
              vidputs                 terminfo(3NCURSES)
              vline                   border(3NCURSES)
              vline_set               border_set(3NCURSES)
              vw_printw               printw(3NCURSES)
              vw_scanw                scanw(3NCURSES)
              vwprintw                printw(3NCURSES)

              vwscanw                 scanw(3NCURSES)
              wadd_wch                add_wch(3NCURSES)
              wadd_wchnstr            add_wchstr(3NCURSES)
              wadd_wchstr             add_wchstr(3NCURSES)
              waddch                  addch(3NCURSES)
              waddchnstr              addchstr(3NCURSES)
              waddchstr               addchstr(3NCURSES)
              waddnstr                addstr(3NCURSES)
              waddnwstr               addwstr(3NCURSES)
              waddstr                 addstr(3NCURSES)
              waddwstr                addwstr(3NCURSES)
              wattr_get               attr(3NCURSES)
              wattr_off               attr(3NCURSES)
              wattr_on                attr(3NCURSES)
              wattr_set               attr(3NCURSES)
              wattroff                attr(3NCURSES)
              wattron                 attr(3NCURSES)
              wattrset                attr(3NCURSES)
              wbkgd                   bkgd(3NCURSES)
              wbkgdset                bkgd(3NCURSES)
              wbkgrnd                 bkgrnd(3NCURSES)
              wbkgrndset              bkgrnd(3NCURSES)
              wborder                 border(3NCURSES)
              wborder_set             border_set(3NCURSES)
              wchgat                  attr(3NCURSES)
              wclear                  clear(3NCURSES)
              wclrtobot               clear(3NCURSES)
              wclrtoeol               clear(3NCURSES)
              wcolor_set              attr(3NCURSES)
              wcursyncup              window(3NCURSES)
              wdelch                  delch(3NCURSES)
              wdeleteln               deleteln(3NCURSES)
              wecho_wchar             add_wch(3NCURSES)
              wechochar               addch(3NCURSES)
              wenclose                mouse(3NCURSES)*
              werase                  clear(3NCURSES)
              wget_wch                get_wch(3NCURSES)
              wget_wstr               get_wstr(3NCURSES)
              wgetbkgrnd              bkgrnd(3NCURSES)
              wgetch                  getch(3NCURSES)
              wgetdelay               opaque(3NCURSES)*
              wgetn_wstr              get_wstr(3NCURSES)
              wgetnstr                getstr(3NCURSES)
              wgetparent              opaque(3NCURSES)*
              wgetscrreg              opaque(3NCURSES)*
              wgetstr                 getstr(3NCURSES)
              whline                  border(3NCURSES)
              whline_set              border_set(3NCURSES)
              win_wch                 in_wch(3NCURSES)
              win_wchnstr             in_wchstr(3NCURSES)
              win_wchstr              in_wchstr(3NCURSES)
              winch                   inch(3NCURSES)
              winchnstr               inchstr(3NCURSES)
              winchstr                inchstr(3NCURSES)
              winnstr                 instr(3NCURSES)
              winnwstr                inwstr(3NCURSES)
              wins_nwstr              ins_wstr(3NCURSES)
              wins_wch                ins_wch(3NCURSES)
              wins_wstr               ins_wstr(3NCURSES)
              winsch                  insch(3NCURSES)
              winsdelln               deleteln(3NCURSES)
              winsertln               deleteln(3NCURSES)
              winsnstr                insstr(3NCURSES)
              winsstr                 insstr(3NCURSES)
              winstr                  instr(3NCURSES)

              winwstr                 inwstr(3NCURSES)
              wmouse_trafo            mouse(3NCURSES)*
              wmove                   move(3NCURSES)
              wnoutrefresh            refresh(3NCURSES)
              wprintw                 printw(3NCURSES)
              wredrawln               refresh(3NCURSES)
              wrefresh                refresh(3NCURSES)
              wresize                 wresize(3NCURSES)*
              wscanw                  scanw(3NCURSES)
              wscrl                   scroll(3NCURSES)
              wsetscrreg              outopts(3NCURSES)
              wstandend               attr(3NCURSES)
              wstandout               attr(3NCURSES)
              wsyncdown               window(3NCURSES)
              wsyncup                 window(3NCURSES)
              wtimeout                inopts(3NCURSES)
              wtouchln                touch(3NCURSES)
              wunctrl                 util(3NCURSES)
              wvline                  border(3NCURSES)
              wvline_set              border_set(3NCURSES)


   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
   parameters, 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

   Routines that return pointers return NULL on error.


   The following  environment  symbols  are  useful  for  customizing  the
   runtime  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
   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 it if it does not happen to be a
   single character.

   The  debugging  library  checks  this  environment  variable  when  the
   application  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.
   However, 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
   descriptions,  e.g.,  xterm  which commonly specifies a 65 line screen.
   For best results, lines and cols should not be specified in a  terminal
   description 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
   multiple-clicking,  you may wish to lengthen this default value because
   the timeout applies to the composed multi-click event as  well  as  the
   individual 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:


   Like COLUMNS, specify the height of  the  screen  in  characters.   See
   COLUMNS for a detailed description.

   This  applies  only  to  the  OS/2 EMX port.  It specifies the order of
   buttons 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
   specified, ncurses uses 132.

   Override  the compiled-in assumption that the terminal's default colors
   are white-on-black (see default_colors(3NCURSES)).   You  may  set  the
   foreground  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
   CreateConsoleScreenBuffer 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

   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.  NCURSES_NO_MAGIC_COOKIE Some
   terminals use a magic-cookie feature which requires special handling to
   make highlighting and other video attributes display properly.  You can
   suppress the highlighting entirely for these terminals by setting  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,
   preventing 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
   control sequences such as flash.

   This setting is obsolete.  Before changes

      *   started with 5.9 patch 20120825 and

      *   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
   purposes, 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)

   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
   nonconventional  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
   emulator  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

   When setting this variable, you should  set  it  to  a  nonzero  value.
   Setting  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

   The argument values, which are defined  in  curses.h,  provide  several
   types   of   information.   When  running  with  traces  enabled,  your
   application 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
   approximation, 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
   information denoted by the TERM environment variable exists.  In either
   case,  setting  it  directs  ncurses to ignore the usual place for this
   information, e.g., /etc/termcap.

   Overrides the directory in which ncurses  searches  for  your  terminal
   description.   This is the simplest, but not the only way to change the
   list of  directories.   The  complete  list  of  directories  in  order

      *   the  last  directory to which ncurses wrote, if any, is searched

      *   the directory specified by the TERMINFO environment variable

      *   $HOME/.terminfo

      *   directories listed in the TERMINFO_DIRS environment variable

      *   one or more directories whose names are configured and  compiled
          into the ncurses library, i.e.,

         *   no   default   value   (corresponding  to  the  TERMINFO_DIRS

         *   /etc/terminfo (corresponding to the TERMINFO variable)

   Specifies a list of directories to search  for  terminal  descriptions.
   The list is separated by colons (i.e., ":") on Unix, semicolons on OS/2

   All of the terminal descriptions are in terminfo form.  Normally  these
   are stored in a directory tree, using subdirectories named by the first
   letter of the terminal names therein.

   If ncurses is built with a hashed database, then  each  entry  in  this
   list can also be the path of the corresponding database file.

   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.

   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

   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:



   Several  different  configurations  are  possible,  depending  on   the
   configure  script  options used when building ncurses.  There are a few
   main options whose effects are visible to  the  applications  developer
   using ncurses:

        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.

        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 define _XOPEN_SOURCE_EXTENDED when compiling for the
        wide-character   library  to  use  the  extended  (wide-character)
        functions.  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-
        character  library's  headers  should  be installed last, to allow
        applications to be built using either library from the same set of

        The  configure  script  renames  the  library.  All of the library
        names have a "t"  appended  to  them  (before  any  "w"  added  by

        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.




        The shared and normal  (static)  library  names  differ  by  their
        suffixes,  e.g.,  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.

        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.


        directory  containing  initialization  files  for   the   terminal
        capability database /etc/terminfo terminal capability database


   terminfo(5)  and  related  pages whose names begin "curs_" for detailed
   routine descriptions.


   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
   termcap 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  mouse(3NCURSES)  manual
   page for details.

   The  ncurses  library  includes  facilities  for  responding  to window
   resizing  events,  e.g.,  when  running   in   an   xterm.    See   the
   resizeterm(3NCURSES)  and  wresize(3NCURSES)  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(3NCURSES)
   key_defined(3NCURSES), and keyok(3NCURSES) 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
   background 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_colors(3NCURSES) manual page for details.

   The  ncurses  library  includes  a  function  for directing application
   output  to  a  printer  attached  to  the  terminal  device.   See  the
   print(3NCURSES) manual page for details.


   The  ncurses  library  is intended to be BASE-level conformant with XSI
   Curses.   The  EXTENDED  XSI  Curses  functionality  (including   color
   support) 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.

   Unlike  other  implementations,  this  one  checks  parameters  such as
   pointers 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.

   This implementation also contains several extensions:

   *   The routine has_key is not part of XPG4, nor is it present in SVr4.
       See the getch(3NCURSES) manual page for details.

   *   The routine slk_attr is not part of XPG4,  nor  is  it  present  in
       SVr4.  See the slk(3NCURSES) manual page for details.

   *   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 mouse(3NCURSES) manual page for

   *   The  routine  mcprint  was  not  present  in  any  previous  curses
       implementation.  See the print(3NCURSES) manual page for details.

   *   The routine wresize is not part of XPG4, nor is it present in SVr4.
       See the wresize(3NCURSES) manual page for details.

   *   The  WINDOW  structure's  internal  details  can  be  hidden   from
       application  programs.   See opaque(3NCURSES) for the discussion of
       is_scrollok, etc.

   *   This  implementation  can  be  configured  to  provide  rudimentary
       support for multi-threaded applications.  See threads(3NCURSES) for

   *   This implementation can also be configured  to  provide  a  set  of
       functions  which  improve  the  ability to manage multiple screens.
       See sp_funcs(3NCURSES) 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
   interface 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>.

   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.



Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.