1curs_initscr(3X)                                              curs_initscr(3X)
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NAME

6       initscr, newterm, endwin, isendwin, set_term, delscreen - curses screen
7       initialization and manipulation routines
8

SYNOPSIS

10       #include <curses.h>
11
12       WINDOW *initscr(void);
13       int endwin(void);
14       bool isendwin(void);
15       SCREEN *newterm(const char *type, FILE *outfd, FILE *infd);
16       SCREEN *set_term(SCREEN *new);
17       void delscreen(SCREEN* sp);
18

DESCRIPTION

20   initscr
21       initscr is normally the first curses routine to call when  initializing
22       a  program.   A few special routines sometimes need to be called before
23       it; these are slk_init(3X), filter, ripoffline, use_env.  For multiple-
24       terminal applications, newterm may be called before initscr.
25
26       The initscr code determines the terminal type and initializes all curs‐
27       es data structures.  initscr also causes the first call to  refresh(3X)
28       to  clear  the  screen.  If errors occur, initscr writes an appropriate
29       error message to standard error and exits; otherwise, a pointer is  re‐
30       turned to stdscr.
31
32   newterm
33       A program that outputs to more than one terminal should use the newterm
34       routine for each terminal instead of initscr.  A program that needs  to
35       inspect capabilities, so it can continue to run in a line-oriented mode
36       if the terminal cannot support a screen-oriented  program,  would  also
37       use newterm.  The routine newterm should be called once for each termi‐
38       nal.  It returns a variable of type SCREEN * which should be saved as a
39       reference to that terminal.  newterm's arguments are
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41       ·   the type of the terminal to be used in place of $TERM,
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43       ·   a file pointer for output to the terminal, and
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45       ·   another file pointer for input from the terminal
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47       If the type parameter is NULL, $TERM will be used.
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49   endwin
50       The  program  must also call endwin for each terminal being used before
51       exiting from curses.  If newterm is called more than once for the  same
52       terminal, the first terminal referred to must be the last one for which
53       endwin is called.
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55       A program should always call endwin before  exiting  or  escaping  from
56       curses mode temporarily.  This routine
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58       ·   resets colors to correspond with the default color pair 0,
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60       ·   moves the cursor to the lower left-hand corner of the screen,
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62       ·   clears  the  remainder of the line so that it uses the default col‐
63           ors,
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65       ·   sets the cursor to normal visibility (see curs_set(3X)),
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67       ·   stops cursor-addressing mode using the exit_ca_mode terminal  capa‐
68           bility,
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70       ·   restores tty modes (see reset_shell_mode(3X)).
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72       Calling refresh(3X) or doupdate(3X) after a temporary escape causes the
73       program to resume visual mode.
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75   isendwin
76       The isendwin routine returns TRUE if endwin has been called without any
77       subsequent calls to wrefresh, and FALSE otherwise.
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79   set_term
80       The  set_term  routine  is  used to switch between different terminals.
81       The screen reference new becomes the new current terminal.  The  previ‐
82       ous  terminal  is  returned  by  the routine.  This is the only routine
83       which manipulates SCREEN pointers; all other routines affect  only  the
84       current terminal.
85
86   delscreen
87       The  delscreen  routine  frees  storage associated with the SCREEN data
88       structure.  The endwin routine does not do this, so delscreen should be
89       called after endwin if a particular SCREEN is no longer needed.
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RETURN VALUE

92       endwin returns the integer ERR upon failure and OK upon successful com‐
93       pletion.
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95       Routines that return pointers always return NULL on error.
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97       X/Open defines no error conditions.  In this implementation
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99       ·   endwin returns an error if the terminal was not initialized.
100
101       ·   newterm returns an error if it cannot allocate the data  structures
102           for  the  screen,  or  for the top-level windows within the screen,
103           i.e., curscr, newscr, or stdscr.
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105       ·   set_term returns no error.
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PORTABILITY

108       These functions were described in the XSI Curses standard, Issue 4.  As
109       of 2015, the current document is X/Open Curses, Issue 7.
110
111   Differences
112       X/Open  specifies that portable applications must not call initscr more
113       than once:
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115       ·   The portable way to use initscr is once only,  using  refresh  (see
116           curs_refresh(3X)) to restore the screen after endwin.
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118       ·   This implementation allows using initscr after endwin.
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120       Old versions of curses, e.g., BSD 4.4, may have returned a null pointer
121       from initscr when an error is detected, rather  than  exiting.   It  is
122       safe but redundant to check the return value of initscr in XSI Curses.
123
124   Unset TERM Variable
125       If  the  TERM variable is missing or empty, initscr uses the value “un‐
126       known”, which normally corresponds to a terminal entry with the generic
127       (gn)  capability.   Generic  entries  are  detected  by  setupterm (see
128       curs_terminfo(3X)) and cannot be used for full-screen operation.  Other
129       implementations may handle a missing/empty TERM variable differently.
130
131   Signal Handlers
132       Quoting from X/Open Curses, section 3.1.1:
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134            Curses  implementations  may  provide  for special handling of the
135            SIGINT, SIGQUIT  and  SIGTSTP  signals  if  their  disposition  is
136            SIG_DFL at the time initscr is called ...
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138            Any  special  handling  for these signals may remain in effect for
139            the life of the process or until the process changes the  disposi‐
140            tion of the signal.
141
142            None  of the Curses functions are required to be safe with respect
143            to signals ...
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145       This implementation establishes signal handlers during  initialization,
146       e.g., initscr or newterm.  Applications which must handle these signals
147       should set up the corresponding handlers  after  initializing  the  li‐
148       brary:
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150       SIGINT
151            The  handler  attempts to cleanup the screen on exit.  Although it
152            usually works as expected, there are limitations:
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154            ·   Walking the SCREEN list is unsafe, since all  list  management
155                is done without any signal blocking.
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157            ·   On systems which have REENTRANT turned on, set_term uses func‐
158                tions which could deadlock or misbehave in other ways.
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160            ·   endwin calls other functions, many of which use stdio or other
161                library functions which are clearly unsafe.
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163       SIGTERM
164            This  uses  the same handler as SIGINT, with the same limitations.
165            It is not mentioned in X/Open Curses, but  is  more  suitable  for
166            this purpose than SIGQUIT (which is used in debugging).
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168       SIGTSTP
169            This  handles the stop signal, used in job control.  When resuming
170            the process,  this  implementation  discards  pending  input  with
171            flushinput  (see  curs_util(3X)), and repaints the screen assuming
172            that it has been completely altered.  It also  updates  the  saved
173            terminal modes with def_shell_mode (see curs_kernel(3X)).
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175       SIGWINCH
176            This  handles  the  window-size  changes which were ignored in the
177            standardization efforts.  The handler sets a  (signal-safe)  vari‐
178            able  which  is  later  tested in wgetch (see curs_getch(3X)).  If
179            keypad has been enabled for the corresponding window,  wgetch  re‐
180            turns  the  key symbol KEY_RESIZE.  At the same time, wgetch calls
181            resizeterm to adjust the standard screen stdscr, and update  other
182            data such as LINES and COLS.
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SEE ALSO

185       curses(3X),  curs_kernel(3X), curs_refresh(3X), curs_slk(3X), curs_ter‐
186       minfo(3X), curs_util(3X), curs_variables(3X).
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190                                                              curs_initscr(3X)
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