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delscreen(3x)

curs_initscr(3x)                 Library calls                curs_initscr(3x)

NAME
       initscr,  newterm,  endwin, isendwin, set_term, delscreen - initialize,
       manipulate, or tear down curses terminal interface

SYNOPSIS
       #include <ncursesw/curses.h>

       WINDOW * initscr(void);
       int endwin(void);

       bool isendwin(void);

       SCREEN * newterm(const char * type, FILE * outf, FILE * inf);
       SCREEN * set_term(SCREEN * new);
       void delscreen(SCREEN * sp);

DESCRIPTION
   initscr
       initscr determines the terminal  type  and  initializes  the  library's
       SCREEN,  WINDOW,  and  other data structures.  It is normally the first
       curses function call a program performs.  However, an application  with
       unusual needs might employ a few other curses functions beforehand:

       •   slk_init(3X) to set up soft-label keys;

       •   filter(3X)  if  the  program  is  designed  to operate in a process
           pipeline;

       •   ripoffline(3X) to reserve up to five lines at the top and/or bottom
           of the screen from management by stdscr, the standard  curses  win‐
           dow; and

       •   use_env(3X)  and/or  use_tioctl(3X) to configure use of the process
           environment and operating system's terminal  driver,  respectively,
           when determining the dimensions of the terminal display.

       Further,  a  curses  program  might call newterm prior to or instead of
       initscr in two specialized cases described in its subsection below.

       initscr causes the first refresh(3X) call to clear the screen.  If  er‐
       rors  occur,  initscr  writes  an appropriate diagnostic message to the
       standard error stream and exits; otherwise, it  returns  a  pointer  to
       stdscr.

   newterm
       An application that manages multiple terminals should call newterm once
       for each such device instead of initscr.  newterm's arguments are

       •   the  type  of the associated terminal, or a null pointer to use the
           TERM environment variable;

       •   an output stream outf connected to the terminal; and

       •   an input stream inf connected to the terminal.  It returns a  vari‐
           able of pointer-to-SCREEN type, which should be saved for later use
           with set_term and delscreen.

       newterm passes the file descriptor of the output stream to the terminfo
       function setupterm(3X), which returns a pointer to a TERMINAL structure
       that newterm stores in the SCREEN it returns to the application.

       An application that needs to inspect a terminal type's capabilities, so
       that  it  can  continue  to run in a line-oriented mode if the terminal
       cannot support a screen-oriented program, would also use  newterm.   If
       at most one terminal connection is needed, the programmer could perform
       such  a  capability  test,  decide which mode in which to operate, then
       call delscreen on the pointer returned by newterm, and proceed with ei‐
       ther initscr or a non-curses interface.

   endwin
       The program must also call endwin for each terminal being  used  before
       exiting  from curses.  If newterm is called more than once for the same
       terminal, the first terminal referred to must be the last one for which
       endwin is called.

       A program should always call endwin before exiting the  application  or
       temporarily suspending curses's management of the terminal.  endwin:

       •   resets colors to correspond with the default color pair 0,

       •   moves the cursor to the lower left-hand corner of the screen,

       •   clears  the  remainder of the line so that it uses the default col‐
           ors,

       •   sets the cursor to normal visibility (see curs_set(3X)),

       •   if applicable, stops cursor-addressing mode using the  exit_ca_mode
           (rmcup) terminal capability, and

       •   restores terminal modes (see reset_shell_mode(3X)).

       Calling refresh(3X) or doupdate(3X) after a temporary suspension causes
       curses to resume managing the terminal.

   isendwin
       isendwin  returns TRUE if endwin has been called without any subsequent
       calls to wrefresh(3X), and FALSE otherwise.

   set_term
       set_term re-orients the curses library's operations to another terminal
       when the application has arranged to manage more than one with newterm.
       set_term expects a SCREEN pointer previously returned by newterm as  an
       argument,  and  returns  the previous one.  set_term is the only curses
       API function that manipulates SCREEN pointers; all others  affect  only
       the current terminal.

   delscreen
       delscreen  frees  the storage backing the supplied SCREEN pointer argu‐
       ment.  endwin does not, so that an application can  resume  managing  a
       terminal  with  curses after a (possibly conditional or temporary) sus‐
       pension; see curs_kernel(3X).  Call delscreen after endwin when a  par‐
       ticular SCREEN structure is no longer needed.

RETURN VALUE
       delscreen  returns  no  value.  endwin returns OK on success and ERR on
       failure.  isendwin returns TRUE or FALSE as described above.

       In ncurses,

       •   endwin returns ERR if

           •   the terminal was not initialized,

           •   it is called more than once without updating the screen, or

           •   its call of reset_shell_mode(3X) returns ERR.

       •   newterm returns ERR if it cannot allocate storage  for  the  SCREEN
           structure  or  the  WINDOW structures automatically associated with
           it: curscr, newscr, and stdscr.

       Functions that return pointers  return  null  pointers  on  error.   In
       ncurses,  set_term  does not fail, and initscr exits the application if
       it does not operate successfully.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:

       box; cbp-1 | cbp-1 l | l .  ATTRIBUTE TYPE ATTRIBUTE VALUE = Availabil‐
       ity   library/ncurses = Stability Uncommitted

NOTES
       ncurses establishes signal handlers when a function that initializes  a
       SCREEN,  either initscr or newterm, is first called.  Applications that
       wish to handle the following signals themselves  should  set  up  their
       corresponding handlers after initializing the screen.

       SIGINT ncurses's  handler attempts to clean up the screen on exit.  Al‐
              though it usually works as expected, there are limitations.

              •   Walking the SCREEN list is unsafe, since all list management
                  is done without any signal blocking.

              •   When an application has been built with the _REENTRANT macro
                  defined (and corresponding system  support),  set_term  uses
                  functions that could deadlock or misbehave in other ways.

              •   endwin  calls other functions, many of which use stdio(3) or
                  other library functions that are clearly unsafe.

       SIGTERM
              ncurses uses the same handler as for SIGINT, with the same limi‐
              tations.  It is not mentioned in  X/Open  Curses,  but  is  more
              suitable  for this purpose than SIGQUIT (which is used in debug‐
              ging).

       SIGTSTP
              ncurses's handler manages the  terminal-generated  stop  signal,
              used  in  job  control.  When resuming the process, ncurses dis‐
              cards pending input with flushinp(3X) and repaints  the  screen,
              assuming  that  it has been completely altered.  It also updates
              the saved terminal modes with def_shell_mode(3X).

       SIGWINCH
              ncurses handles changes to the terminal's window size, a phenom‐
              enon ignored in standardization efforts.   It  sets  a  (signal-
              safe)   variable   that   is  later  tested  by  wgetch(3X)  and
              wget_wch(3X).

              •   wgetch returns the key code KEY_RESIZE.

              •   wget_wch returns KEY_CODE_YES and sets its wch parameter  to
                  KEY_RESIZE.

              At  the  same  time,  ncurses calls resizeterm(3X) to adjust the
              standard screen stdscr, and  update  global  variables  such  as
              LINES and COLS.

              Source  code  for  open source software components in Oracle So‐
              laris can  be  found  at  https://www.oracle.com/downloads/open‐
              source/solaris-source-code-downloads.html.

              This software was built from source available at:
              https://github.com/oracle/solaris-userland

              The original community source was downloaded from:
              https://invisible-mirror.net/archives/ncurses/cur‐
              rent/ncurses-6.5-20250614.tgz

              Further information about this software can be found on the open
              source     community     website     at    https://invisible-is‐
              land.net/ncurses/.

PORTABILITY
       X/Open Curses Issue 4 describes these functions.  It specifies no error
       conditions for them.

   Differences
       X/Open Curses  specifies  that  portable  applications  must  not  call
       initscr more than once.

       •   The  portable way to use initscr is once only, using refresh to re‐
           store the screen after endwin.

       •   ncurses permits use of initscr after endwin.

       initscr in BSD, from its inception (1980)  through  the  Net/2  release
       (1991)  returned  ERR cast to a WINDOW pointer when detecting an error.
       4.4BSD (1995) instead returned a null pointer.  Neither exited the  ap‐
       plication.   It  is  safe  but  redundant  to check the return value of
       initscr in X/Open Curses.

       Calling endwin does not dispose of the memory allocated by  initscr  or
       newterm.  Deleting a SCREEN provides a way to do this.

       •   X/Open  Curses  does not say what happens to WINDOWs when delscreen
           “frees storage associated with the SCREEN” nor does the SVr4  docu‐
           mentation  help,  adding that it should be called after endwin if a
           SCREEN is no longer needed.

       •   However, WINDOWs are implicitly associated with a SCREEN, so it  is
           reasonable to expect delscreen to dispose of them.

       •   SVr4  deletes  the  standard WINDOW structures stdscr and curscr as
           well as a work area newscr.  It ignores other windows.

       •   Since version 4.0 (1996), ncurses has maintained a list of all win‐
           dows for each screen, using that information to delete  those  win‐
           dows when delscreen is called.

       •   NetBSD  copied  this  feature of ncurses in 2001.  PDCurses follows
           the SVr4 model, deleting only the standard WINDOW structures.

   High-level versus Low-level
       Different implementations may disagree  regarding  the  level  of  some
       functions.  For example, SCREEN (returned by newterm) and TERMINAL (re‐
       turned  by  setupterm(3X)) hold file descriptors for the output stream.
       If an application switches screens using set_term, or  switches  termi‐
       nals  using set_curterm(3X), applications which use the output file de‐
       scriptor can have different behavior depending on which structure holds
       the corresponding descriptor.

       •   NetBSD's  baudrate  function  uses  the  descriptor  in   TERMINAL.
           ncurses and SVr4 use the descriptor in SCREEN.

       •   NetBSD  and ncurses use the descriptor in TERMINAL for terminal I/O
           modes, e.g., def_shell_mode(3X), def_prog_mode(3X).  SVr4 uses  the
           descriptor in SCREEN.

   Unset TERM Environment Variable
       If  the  TERM  variable  is  not set in the environment or has an empty
       value, initscr uses the value “unknown”, which normally corresponds  to
       a terminal entry with the generic (gn) capability.  Generic entries are
       detected by setupterm(3X) and cannot be used for full-screen operation.
       Other  implementations may handle a missing or empty TERM variable dif‐
       ferently.

   Signal Handlers
       Quoting X/Open Curses Issue 7, section 3.1.1:

            Curses implementations may provide for  special  handling  of  the
            SIGINT,  SIGQUIT,  and  SIGTSTP  signals  if  their disposition is
            SIG_DFL at the time initscr() is called...

            Any special handling for these signals may remain  in  effect  for
            the  life of the process or until the process changes the disposi‐
            tion of the signal.

            None of the Curses functions are required to be safe with  respect
            to signals...

       Section “NOTES” above discusses ncurses's signal handlers.

HISTORY
       4BSD (1980) introduced initscr and endwin.

       SVr2 (1984) added newterm and set_term.

       SVr3.1 (1987) supplied delscreen and isendwin.

SEE ALSO
       curses(3X),     curs_kernel(3X),     curs_refresh(3X),    curs_slk(3X),
       curs_terminfo(3X), curs_util(3X), curs_variables(3X)


ncurses 6.5                       2025-03-15                  curs_initscr(3x)
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