NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | PORTABILITY | SEE ALSO | COLOPHON

curs_initscr(3X)                                            curs_initscr(3X)

NAME         top

       initscr, newterm, endwin, isendwin, set_term, delscreen - curses
       screen initialization and manipulation routines

SYNOPSIS         top

       #include <curses.h>

       WINDOW *initscr(void);
       int endwin(void);
       bool isendwin(void);
       SCREEN *newterm(char *type, FILE *outfd, FILE *infd);
       SCREEN *set_term(SCREEN *new);
       void delscreen(SCREEN* sp);

DESCRIPTION         top

   initscr
       initscr is normally the first curses routine to call when
       initializing a program.  A few special routines sometimes need to be
       called before it; these are slk_init(3X), filter, ripoffline,
       use_env.  For multiple-terminal applications, newterm may be called
       before initscr.

       The initscr code determines the terminal type and initializes all
       curses data structures.  initscr also causes the first call to
       refresh(3X) to clear the screen.  If errors occur, initscr writes an
       appropriate error message to standard error and exits; otherwise, a
       pointer is returned to stdscr.

   newterm
       A program that outputs to more than one terminal should use the
       newterm routine for each terminal instead of initscr.  A program that
       needs to inspect capabilities, so it can continue to run in a line-
       oriented mode if the terminal cannot support a screen-oriented
       program, would also use newterm.  The routine newterm should be
       called once for each terminal.  It returns a variable of type SCREEN
       * which should be saved as a reference to that terminal.  newterm's
       arguments are

       ·   the type of the terminal to be used in place of $TERM,

       ·   a file pointer for output to the terminal, and

       ·   another file pointer for input from the terminal

       If the type parameter is NULL, $TERM will be used.

   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 or escaping from
       curses mode temporarily.  This routine

       ·   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
           colors,

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

       ·   stops cursor-addressing mode using the exit_ca_mode terminal
           capability,

       ·   restores tty modes (see reset_shell_mode(3X)).

       Calling refresh(3X) or doupdate(3X) after a temporary escape causes
       the program to resume visual mode.

   isendwin
       The isendwin routine returns TRUE if endwin has been called without
       any subsequent calls to wrefresh, and FALSE otherwise.

   set_term
       The set_term routine is used to switch between different terminals.
       The screen reference new becomes the new current terminal.  The
       previous terminal is returned by the routine.  This is the only
       routine which manipulates SCREEN pointers; all other routines affect
       only the current terminal.

   delscreen
       The delscreen routine frees storage associated with the SCREEN data
       structure.  The endwin routine does not do this, so delscreen should
       be called after endwin if a particular SCREEN is no longer needed.

RETURN VALUE         top

       endwin returns the integer ERR upon failure and OK upon successful
       completion.

       Routines that return pointers always return NULL on error.

       X/Open defines no error conditions.  In this implementation

       ·   endwin returns an error if the terminal was not initialized.

       ·   newterm returns an error if it cannot allocate the data
           structures for the screen, or for the top-level windows within
           the screen, i.e., curscr, newscr, or stdscr.

       ·   set_term returns no error.

PORTABILITY         top

       These functions were described in the XSI Curses standard, Issue 4.
       As of 2015, the current document is X/Open Curses, Issue 7.

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

       ·   The portable way to use initscr is once only, using refresh (see
           curs_refresh(3X)) to restore the screen after endwin.

       ·   This implementation allows using initscr after endwin.

       Old versions of curses, e.g., BSD 4.4, may have returned a null
       pointer from initscr when an error is detected, rather than exiting.
       It is safe but redundant to check the return value of initscr in XSI
       Curses.

   Unset TERM Variable
       If the TERM variable is missing or empty, initscr uses the value
       “unknown”, which normally corresponds to a terminal entry with the
       generic (gn) capability.  Generic entries are detected by setupterm
       (see curs_terminfo(3X)) and cannot be used for full-screen operation.
       Other implementations may handle a missing/empty TERM variable
       differently.

   Signal Handlers
       Quoting from X/Open Curses, 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
            disposition of the signal.

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

       This implementation establishes signal handlers during
       initialization, e.g., initscr or newterm.  Applications which must
       handle these signals should set up the corresponding handlers after
       initializing the library:

       SIGINT
            The handler attempts to cleanup the screen on exit.  Although it
            usually works as expected, there are limitations:

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

            ·   On systems which have REENTRANT turned on, set_term uses
                functions which could deadlock or misbehave in other ways.

            ·   endwin calls other functions, many of which use stdio or
                other library functions which are clearly unsafe.

       SIGTERM
            This uses the same handler as SIGINT, with the same limitations.
            It is not mentioned in X/Open Curses, but is more suitable for
            this purpose than SIGQUIT (which is used in debugging).

       SIGTSTP
            This handles the stop signal, used in job control.  When
            resuming the process, this implementation discards pending input
            with flushinput (see curs_util(3X)), and repaints the screen
            assuming that it has been completely altered.  It also updates
            the saved terminal modes with def_shell_mode (see
            curs_kernel(3X)).

       SIGWINCH
            This handles the window-size changes which were initially
            ignored in the standardization efforts.  The handler sets a
            (signal-safe) variable which is later tested in wgetch (see
            curs_getch(3X)).  If keypad has been enabled for the
            corresponding window, wgetch returns the key symbol KEY_RESIZE.
            At the same time, wgetch calls resizeterm to adjust the standard
            screen stdscr, and update other data such as LINES and COLS.

SEE ALSO         top

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

COLOPHON         top

       This page is part of the ncurses (new curses) project.  Information
       about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have a
       bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
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       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2017-05-03.  If you
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       COLOPHON (which is not part of the original manual page), send a mail
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                                                            curs_initscr(3X)