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42 <H1 class="no-header">curs_initscr 3x 2023-07-01 ncurses 6.4 Library calls</H1>
44 <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>initscr</STRONG>, <STRONG>newterm</STRONG>, <STRONG>endwin</STRONG>, <STRONG>isendwin</STRONG>, <STRONG>set_term</STRONG>, <STRONG>delscreen</STRONG> - <STRONG>curses</STRONG> screen
51 initialization and manipulation routines
54 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
55 <STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
57 <STRONG>WINDOW</STRONG> <STRONG>*initscr(void);</STRONG>
58 <STRONG>int</STRONG> <STRONG>endwin(void);</STRONG>
60 <STRONG>bool</STRONG> <STRONG>isendwin(void);</STRONG>
62 <STRONG>SCREEN</STRONG> <STRONG>*newterm(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>type</EM><STRONG>,</STRONG> <STRONG>FILE</STRONG> <STRONG>*</STRONG><EM>outf</EM><STRONG>,</STRONG> <STRONG>FILE</STRONG> <STRONG>*</STRONG><EM>inf</EM><STRONG>);</STRONG>
63 <STRONG>SCREEN</STRONG> <STRONG>*set_term(SCREEN</STRONG> <STRONG>*</STRONG><EM>new</EM><STRONG>);</STRONG>
64 <STRONG>void</STRONG> <STRONG>delscreen(SCREEN*</STRONG> <EM>sp</EM><STRONG>);</STRONG>
67 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
69 </PRE><H3><a name="h3-initscr">initscr</a></H3><PRE>
70 <STRONG>initscr</STRONG> is normally the first <STRONG>curses</STRONG> routine to call when initializing
71 a program. A few special routines sometimes need to be called before
72 it; these are <STRONG><A HREF="curs_slk.3x.html">slk_init(3x)</A></STRONG>, <STRONG>filter</STRONG>, <STRONG>ripoffline</STRONG>, <STRONG>use_env</STRONG>. For multiple-
73 terminal applications, <STRONG>newterm</STRONG> may be called before <STRONG>initscr</STRONG>.
75 The initscr code determines the terminal type and initializes all <STRONG>curs-</STRONG>
76 <STRONG>es</STRONG> data structures. <STRONG>initscr</STRONG> also causes the first call to <STRONG><A HREF="curscurs_refresh.3x.html">refresh(3x)</A></STRONG>
77 to clear the screen. If errors occur, <STRONG>initscr</STRONG> writes an appropriate
78 error message to standard error and exits; otherwise, a pointer is re-
79 turned to <STRONG>stdscr</STRONG>.
82 </PRE><H3><a name="h3-newterm">newterm</a></H3><PRE>
83 A program that outputs to more than one terminal should use the <STRONG>newterm</STRONG>
84 routine for each terminal instead of <STRONG>initscr</STRONG>. A program that needs to
85 inspect capabilities, so it can continue to run in a line-oriented mode
86 if the terminal cannot support a screen-oriented program, would also
87 use <STRONG>newterm</STRONG>.
89 The routine <STRONG>newterm</STRONG> should be called once for each terminal. It re-
90 turns a variable of type <STRONG>SCREEN</STRONG> <STRONG>*</STRONG> which should be saved as a reference
91 to that terminal. <STRONG>newterm</STRONG>'s arguments are
93 <STRONG>o</STRONG> the <EM>type</EM> of the terminal to be used in place of <STRONG>$TERM</STRONG>,
95 <STRONG>o</STRONG> an output stream connected to the terminal, and
97 <STRONG>o</STRONG> an input stream connected to the terminal
99 If the <EM>type</EM> parameter is <STRONG>NULL</STRONG>, <STRONG>$TERM</STRONG> will be used.
101 The file descriptor of the output stream is passed to <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>,
102 which returns a pointer to a <STRONG>TERMINAL</STRONG> structure. <STRONG>newterm</STRONG>'s return val-
103 ue holds a pointer to the <STRONG>TERMINAL</STRONG> structure.
106 </PRE><H3><a name="h3-endwin">endwin</a></H3><PRE>
107 The program must also call <STRONG>endwin</STRONG> for each terminal being used before
108 exiting from <STRONG>curses</STRONG>. If <STRONG>newterm</STRONG> is called more than once for the same
109 terminal, the first terminal referred to must be the last one for which
110 <STRONG>endwin</STRONG> is called.
112 A program should always call <STRONG>endwin</STRONG> before exiting or escaping from
113 <STRONG>curses</STRONG> mode temporarily. This routine
115 <STRONG>o</STRONG> resets colors to correspond with the default color pair 0,
117 <STRONG>o</STRONG> moves the cursor to the lower left-hand corner of the screen,
119 <STRONG>o</STRONG> clears the remainder of the line so that it uses the default col-
122 <STRONG>o</STRONG> sets the cursor to normal visibility (see <STRONG><A HREF="curs_kernel.3x.html">curs_set(3x)</A></STRONG>),
124 <STRONG>o</STRONG> stops cursor-addressing mode using the <EM>exit</EM><STRONG>_</STRONG><EM>ca</EM><STRONG>_</STRONG><EM>mode</EM> terminal capa-
127 <STRONG>o</STRONG> restores tty modes (see <STRONG><A HREF="curs_kernel.3x.html">reset_shell_mode(3x)</A></STRONG>).
129 Calling <STRONG><A HREF="curs_refresh.3x.html">refresh(3x)</A></STRONG> or <STRONG><A HREF="curs_refresh.3x.html">doupdate(3x)</A></STRONG> after a temporary escape causes the
130 program to resume visual mode.
133 </PRE><H3><a name="h3-isendwin">isendwin</a></H3><PRE>
134 The <STRONG>isendwin</STRONG> routine returns <STRONG>TRUE</STRONG> if <STRONG>endwin</STRONG> has been called without any
135 subsequent calls to <STRONG>wrefresh</STRONG>, and <STRONG>FALSE</STRONG> otherwise.
138 </PRE><H3><a name="h3-set_term">set_term</a></H3><PRE>
139 The <STRONG>set_term</STRONG> routine is used to switch between different terminals.
140 The screen reference <EM>new</EM> becomes the new current terminal. The previ-
141 ous terminal is returned by the routine. This is the only routine
142 which manipulates <STRONG>SCREEN</STRONG> pointers; all other routines affect only the
146 </PRE><H3><a name="h3-delscreen">delscreen</a></H3><PRE>
147 The <STRONG>delscreen</STRONG> routine frees storage associated with the <STRONG>SCREEN</STRONG> data
148 structure. The <STRONG>endwin</STRONG> routine does not do this, so <STRONG>delscreen</STRONG> should be
149 called after <STRONG>endwin</STRONG> if a particular <STRONG>SCREEN</STRONG> is no longer needed.
152 </PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
153 <STRONG>endwin</STRONG> returns the integer <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG> upon successful com-
156 Routines that return pointers always return <STRONG>NULL</STRONG> on error.
158 X/Open defines no error conditions. In this implementation
160 <STRONG>o</STRONG> <STRONG>endwin</STRONG> returns an error if the terminal was not initialized.
162 <STRONG>o</STRONG> <STRONG>newterm</STRONG> returns an error if it cannot allocate the data structures
163 for the screen, or for the top-level windows within the screen,
164 i.e., <STRONG>curscr</STRONG>, <STRONG>newscr</STRONG>, or <STRONG>stdscr</STRONG>.
166 <STRONG>o</STRONG> <STRONG>set_term</STRONG> returns no error.
169 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
170 These functions were described in the XSI Curses standard, Issue 4. As
171 of 2015, the current document is X/Open Curses, Issue 7.
174 </PRE><H3><a name="h3-Differences">Differences</a></H3><PRE>
175 X/Open specifies that portable applications must not call <STRONG>initscr</STRONG> more
178 <STRONG>o</STRONG> The portable way to use <STRONG>initscr</STRONG> is once only, using <STRONG>refresh</STRONG> (see
179 <STRONG><A HREF="curs_refresh.3x.html">curs_refresh(3x)</A></STRONG>) to restore the screen after <STRONG>endwin</STRONG>.
181 <STRONG>o</STRONG> This implementation allows using <STRONG>initscr</STRONG> after <STRONG>endwin</STRONG>.
183 Old versions of curses, e.g., BSD 4.4, would return a null pointer from
184 <STRONG>initscr</STRONG> when an error is detected, rather than exiting. It is safe but
185 redundant to check the return value of <STRONG>initscr</STRONG> in XSI Curses.
187 Calling <STRONG>endwin</STRONG> does not dispose of the memory allocated in <STRONG>initscr</STRONG> or
188 <STRONG>newterm</STRONG>. Deleting a <STRONG>SCREEN</STRONG> provides a way to do this:
190 <STRONG>o</STRONG> X/Open Curses does not say what happens to <STRONG>WINDOW</STRONG>s when <STRONG>delscreen</STRONG>
191 "frees storage associated with the <STRONG>SCREEN</STRONG>" nor does the SVr4 docu-
192 mentation help, adding that it should be called after <STRONG>endwin</STRONG> if a
193 <STRONG>SCREEN</STRONG> is no longer needed.
195 <STRONG>o</STRONG> However, <STRONG>WINDOW</STRONG>s are implicitly associated with a <STRONG>SCREEN</STRONG>. so that
196 it is reasonable to expect <STRONG>delscreen</STRONG> to deal with these.
198 <STRONG>o</STRONG> SVr4 curses deletes the standard <STRONG>WINDOW</STRONG> structures <STRONG>stdscr</STRONG> and
199 <STRONG>curscr</STRONG> as well as a work area <STRONG>newscr</STRONG>. SVr4 curses ignores other
202 <STRONG>o</STRONG> Since version 4.0 (1996), ncurses has maintained a list of all win-
203 dows for each screen, using that information to delete those win-
204 dows when <STRONG>delscreen</STRONG> is called.
206 <STRONG>o</STRONG> NetBSD copied this feature of ncurses in 2001. PDCurses follows
207 the SVr4 model, deleting only the standard <STRONG>WINDOW</STRONG> structures.
210 </PRE><H3><a name="h3-High-level-versus-low-level">High-level versus low-level</a></H3><PRE>
211 Different implementations may disagree regarding the level of some
212 functions. For example, <STRONG>SCREEN</STRONG> (returned by <STRONG>newterm</STRONG>) and <STRONG>TERMINAL</STRONG> (re-
213 turned by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>) hold file descriptors for the output stream.
214 If an application switches screens using <STRONG>set_term</STRONG>, or switches termi-
215 nals using <STRONG><A HREF="curs_terminfo.3x.html">set_curterm(3x)</A></STRONG>, applications which use the output file de-
216 scriptor can have different behavior depending on which structure holds
217 the corresponding descriptor.
221 <STRONG>o</STRONG> NetBSD's <STRONG><A HREF="curs_termattrs.3x.html">baudrate(3x)</A></STRONG> function uses the descriptor in <STRONG>TERMINAL</STRONG>.
222 <STRONG>ncurses</STRONG> and SVr4 use the descriptor in <STRONG>SCREEN</STRONG>.
224 <STRONG>o</STRONG> NetBSD and <STRONG>ncurses</STRONG> use the descriptor in <STRONG>TERMINAL</STRONG> for terminal I/O
225 modes, e.g., <STRONG><A HREF="curs_kernel.3x.html">def_shell_mode(3x)</A></STRONG>, <STRONG><A HREF="curs_kernel.3x.html">def_prog_mode(3x)</A></STRONG>. SVr4 curses
226 uses the descriptor in <STRONG>SCREEN</STRONG>.
229 </PRE><H3><a name="h3-Unset-TERM-Variable">Unset TERM Variable</a></H3><PRE>
230 If the TERM variable is missing or empty, <STRONG>initscr</STRONG> uses the value "un-
231 known", which normally corresponds to a terminal entry with the <EM>generic</EM>
232 (<EM>gn</EM>) capability. Generic entries are detected by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG> and
233 cannot be used for full-screen operation. Other implementations may
234 handle a missing/empty TERM variable differently.
237 </PRE><H3><a name="h3-Signal-Handlers">Signal Handlers</a></H3><PRE>
238 Quoting from X/Open Curses, section 3.1.1:
240 <EM>Curses</EM> <EM>implementations</EM> <EM>may</EM> <EM>provide</EM> <EM>for</EM> <EM>special</EM> <EM>handling</EM> <EM>of</EM> <EM>the</EM>
241 <STRONG>SIGINT</STRONG><EM>,</EM> <STRONG>SIGQUIT</STRONG> <EM>and</EM> <STRONG>SIGTSTP</STRONG> <EM>signals</EM> <EM>if</EM> <EM>their</EM> <EM>disposition</EM> <EM>is</EM>
242 <STRONG>SIG_DFL</STRONG> <EM>at</EM> <EM>the</EM> <EM>time</EM> <STRONG>initscr</STRONG> <EM>is</EM> <EM>called</EM> ...
244 <EM>Any</EM> <EM>special</EM> <EM>handling</EM> <EM>for</EM> <EM>these</EM> <EM>signals</EM> <EM>may</EM> <EM>remain</EM> <EM>in</EM> <EM>effect</EM> <EM>for</EM>
245 <EM>the</EM> <EM>life</EM> <EM>of</EM> <EM>the</EM> <EM>process</EM> <EM>or</EM> <EM>until</EM> <EM>the</EM> <EM>process</EM> <EM>changes</EM> <EM>the</EM>
246 <EM>disposition</EM> <EM>of</EM> <EM>the</EM> <EM>signal.</EM>
248 <EM>None</EM> <EM>of</EM> <EM>the</EM> <EM>Curses</EM> <EM>functions</EM> <EM>are</EM> <EM>required</EM> <EM>to</EM> <EM>be</EM> <EM>safe</EM> <EM>with</EM> <EM>respect</EM>
249 <EM>to</EM> <EM>signals</EM> ...
251 This implementation establishes signal handlers during initialization,
252 e.g., <STRONG>initscr</STRONG> or <STRONG>newterm</STRONG>. Applications which must handle these signals
253 should set up the corresponding handlers <EM>after</EM> initializing the li-
256 <STRONG>SIGINT</STRONG>
257 The handler <EM>attempts</EM> to cleanup the screen on exit. Although it
258 <EM>usually</EM> works as expected, there are limitations:
260 <STRONG>o</STRONG> Walking the <STRONG>SCREEN</STRONG> list is unsafe, since all list management
261 is done without any signal blocking.
263 <STRONG>o</STRONG> On systems which have <STRONG>REENTRANT</STRONG> turned on, <STRONG>set_term</STRONG> uses func-
264 tions which could deadlock or misbehave in other ways.
266 <STRONG>o</STRONG> <STRONG>endwin</STRONG> calls other functions, many of which use stdio or other
267 library functions which are clearly unsafe.
269 <STRONG>SIGTERM</STRONG>
270 This uses the same handler as <STRONG>SIGINT</STRONG>, with the same limitations.
271 It is not mentioned in X/Open Curses, but is more suitable for
272 this purpose than <STRONG>SIGQUIT</STRONG> (which is used in debugging).
274 <STRONG>SIGTSTP</STRONG>
275 This handles the <EM>stop</EM> signal, used in job control. When resuming
276 the process, this implementation discards pending input with
277 <STRONG>flushinput</STRONG> (see <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>), and repaints the screen assuming
278 that it has been completely altered. It also updates the saved
279 terminal modes with <STRONG>def_shell_mode</STRONG> (see <STRONG><A HREF="curs_kernel.3x.html">curs_kernel(3x)</A></STRONG>).
281 <STRONG>SIGWINCH</STRONG>
282 This handles the window-size changes which were ignored in the
283 standardization efforts. The handler sets a (signal-safe) vari-
284 able which is later tested in <STRONG>wgetch</STRONG> (see <STRONG><A HREF="curs_getch.3x.html">curs_getch(3x)</A></STRONG>). If
285 <STRONG>keypad</STRONG> has been enabled for the corresponding window, <STRONG>wgetch</STRONG> re-
286 turns the key symbol <STRONG>KEY_RESIZE</STRONG>. At the same time, <STRONG>wgetch</STRONG> calls
287 <STRONG>resizeterm</STRONG> to adjust the standard screen <STRONG>stdscr</STRONG>, and update other
288 data such as <STRONG>LINES</STRONG> and <STRONG>COLS</STRONG>.
291 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
292 <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_kernel.3x.html">curs_kernel(3x)</A></STRONG>, <STRONG><A HREF="curs_refresh.3x.html">curs_refresh(3x)</A></STRONG>, <STRONG><A HREF="curs_slk.3x.html">curs_slk(3x)</A></STRONG>, <STRONG>curs_ter-</STRONG>
293 <STRONG><A HREF="curs_terminfo.3x.html">minfo(3x)</A></STRONG>, <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>.
297 ncurses 6.4 2023-07-01 <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>
301 <li><a href="#h2-NAME">NAME</a></li>
302 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
303 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
305 <li><a href="#h3-initscr">initscr</a></li>
306 <li><a href="#h3-newterm">newterm</a></li>
307 <li><a href="#h3-endwin">endwin</a></li>
308 <li><a href="#h3-isendwin">isendwin</a></li>
309 <li><a href="#h3-set_term">set_term</a></li>
310 <li><a href="#h3-delscreen">delscreen</a></li>
313 <li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
314 <li><a href="#h2-PORTABILITY">PORTABILITY</a>
316 <li><a href="#h3-Differences">Differences</a></li>
317 <li><a href="#h3-High-level-versus-low-level">High-level versus low-level</a></li>
318 <li><a href="#h3-Unset-TERM-Variable">Unset TERM Variable</a></li>
319 <li><a href="#h3-Signal-Handlers">Signal Handlers</a></li>
322 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>