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42 <H1 class="no-header">curs_initscr 3x 2023-09-30 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> - initialize,
51 manipulate, or tear down <EM>curses</EM> terminal interface
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
76 <STRONG>curses</STRONG> data structures. <STRONG>initscr</STRONG> also causes the first call to
77 <STRONG><A HREF="curs_refresh.3x.html">refresh(3x)</A></STRONG> to clear the screen. If errors occur, <STRONG>initscr</STRONG> writes an
78 appropriate error message to standard error and exits; otherwise, a
79 pointer is returned 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
90 returns a variable of type <STRONG>SCREEN</STRONG> <STRONG>*</STRONG> which should be saved as a
91 reference 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
103 value 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
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
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
141 previous 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
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
192 documentation help, adding that it should be called after <STRONG>endwin</STRONG> if
193 a <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
203 windows for each screen, using that information to delete those
204 windows 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>
213 (returned by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>) hold file descriptors for the output
214 stream. If an application switches screens using <STRONG>set_term</STRONG>, or switches
215 terminals using <STRONG><A HREF="curs_terminfo.3x.html">set_curterm(3x)</A></STRONG>, applications which use the output file
216 descriptor can have different behavior depending on which structure
217 holds 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
231 "unknown", which normally corresponds to a terminal entry with the
232 <EM>generic</EM> (<EM>gn</EM>) capability. Generic entries are detected by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>
233 and cannot be used for full-screen operation. Other implementations
234 may 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 Issue 7, section 3.1.1:
240 Curses implementations may provide for special handling of the
241 SIGINT, SIGQUIT, and SIGTSTP signals if their disposition is
242 SIG_DFL at the time <EM>initscr</EM> is called...
244 Any special handling for these signals may remain in effect for
245 the life of the process or until the process changes the
246 disposition of the signal.
248 None of the Curses functions are required to be safe with respect
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
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
264 functions 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)
284 variable 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>
286 returns 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>,
293 <STRONG><A HREF="curs_terminfo.3x.html">curs_terminfo(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 2023-09-30 <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>