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<H1 class="no-header">curs_initscr 3x 2024-04-20 ncurses 6.5 Library calls</H1>
<PRE>
<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>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
<STRONG>initscr</STRONG>, <STRONG>newterm</STRONG>, <STRONG>endwin</STRONG>, <STRONG>isendwin</STRONG>, <STRONG>set_term</STRONG>, <STRONG>delscreen</STRONG> - initialize,
manipulate, or tear down <EM>curses</EM> terminal interface
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>WINDOW</STRONG> <STRONG>*initscr(void);</STRONG>
<STRONG>int</STRONG> <STRONG>endwin(void);</STRONG>
<STRONG>bool</STRONG> <STRONG>isendwin(void);</STRONG>
<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>
<STRONG>SCREEN</STRONG> <STRONG>*set_term(SCREEN</STRONG> <STRONG>*</STRONG><EM>new</EM><STRONG>);</STRONG>
<STRONG>void</STRONG> <STRONG>delscreen(SCREEN*</STRONG> <EM>sp</EM><STRONG>);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
</PRE><H3><a name="h3-initscr">initscr</a></H3><PRE>
<STRONG>initscr</STRONG> is normally the first <STRONG>curses</STRONG> routine to call when initializing
a program. A few special routines sometimes need to be called before
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-
terminal applications, <STRONG>newterm</STRONG> may be called before <STRONG>initscr</STRONG>.
The initscr code determines the terminal type and initializes all
<STRONG>curses</STRONG> data structures. <STRONG>initscr</STRONG> also causes the first call to
<STRONG><A HREF="curs_refresh.3x.html">refresh(3x)</A></STRONG> to clear the screen. If errors occur, <STRONG>initscr</STRONG> writes an
appropriate error message to standard error and exits; otherwise, a
pointer is returned to <STRONG>stdscr</STRONG>.
</PRE><H3><a name="h3-newterm">newterm</a></H3><PRE>
A program that outputs to more than one terminal should use the <STRONG>newterm</STRONG>
routine for each terminal instead of <STRONG>initscr</STRONG>. 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 <STRONG>newterm</STRONG>.
The routine <STRONG>newterm</STRONG> should be called once for each terminal. It
returns a variable of type <EM>SCREEN</EM> <EM>*</EM> which should be saved as a
reference to that terminal. <STRONG>newterm</STRONG>'s arguments are
<STRONG>o</STRONG> the <EM>type</EM> of the terminal to be used in place of <STRONG>$TERM</STRONG>,
<STRONG>o</STRONG> an output stream connected to the terminal, and
<STRONG>o</STRONG> an input stream connected to the terminal
If the <EM>type</EM> parameter is <STRONG>NULL</STRONG>, <STRONG>$TERM</STRONG> will be used.
The file descriptor of the output stream is passed to <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>,
which returns a pointer to a <EM>TERMINAL</EM> structure. <STRONG>newterm</STRONG>'s return
value holds a pointer to the <EM>TERMINAL</EM> structure.
</PRE><H3><a name="h3-endwin">endwin</a></H3><PRE>
The program must also call <STRONG>endwin</STRONG> for each terminal being used before
exiting from <STRONG>curses</STRONG>. If <STRONG>newterm</STRONG> is called more than once for the same
terminal, the first terminal referred to must be the last one for which
<STRONG>endwin</STRONG> is called.
A program should always call <STRONG>endwin</STRONG> before exiting or escaping from
<STRONG>curses</STRONG> mode temporarily. This routine
<STRONG>o</STRONG> resets colors to correspond with the default color pair 0,
<STRONG>o</STRONG> moves the cursor to the lower left-hand corner of the screen,
<STRONG>o</STRONG> clears the remainder of the line so that it uses the default
colors,
<STRONG>o</STRONG> sets the cursor to normal visibility (see <STRONG><A HREF="curs_kernel.3x.html">curs_set(3x)</A></STRONG>),
<STRONG>o</STRONG> stops cursor-addressing mode using the <EM>exit</EM><STRONG>_</STRONG><EM>ca</EM><STRONG>_</STRONG><EM>mode</EM> terminal
capability,
<STRONG>o</STRONG> restores tty modes (see <STRONG><A HREF="curs_kernel.3x.html">reset_shell_mode(3x)</A></STRONG>).
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
program to resume visual mode.
</PRE><H3><a name="h3-isendwin">isendwin</a></H3><PRE>
The <STRONG>isendwin</STRONG> routine returns <STRONG>TRUE</STRONG> if <STRONG>endwin</STRONG> has been called without any
subsequent calls to <STRONG>wrefresh</STRONG>, and <STRONG>FALSE</STRONG> otherwise.
</PRE><H3><a name="h3-set_term">set_term</a></H3><PRE>
The <STRONG>set_term</STRONG> routine is used to switch between different terminals.
The screen reference <EM>new</EM> becomes the new current terminal. The
previous terminal is returned by the routine. This is the only routine
which manipulates <EM>SCREEN</EM> pointers; all other routines affect only the
current terminal.
</PRE><H3><a name="h3-delscreen">delscreen</a></H3><PRE>
The <STRONG>delscreen</STRONG> routine frees storage associated with the <EM>SCREEN</EM> data
structure. The <STRONG>endwin</STRONG> routine does not do this, so <STRONG>delscreen</STRONG> should be
called after <STRONG>endwin</STRONG> if a particular <EM>SCREEN</EM> is no longer needed.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
<STRONG>endwin</STRONG> returns the integer <STRONG>ERR</STRONG> upon failure and <STRONG>OK</STRONG> upon successful
completion.
Routines that return pointers always return <STRONG>NULL</STRONG> on error.
X/Open defines no error conditions. In this implementation
<STRONG>o</STRONG> <STRONG>endwin</STRONG> returns an error if
<STRONG>o</STRONG> the terminal was not initialized, or
<STRONG>o</STRONG> <STRONG>endwin</STRONG> is called more than once without updating the screen, or
<STRONG>o</STRONG> <STRONG><A HREF="curs_kernel.3x.html">reset_shell_mode(3x)</A></STRONG> returns an error.
<STRONG>o</STRONG> <STRONG>newterm</STRONG> returns an error if it cannot allocate the data structures
for the screen, or for the top-level windows within the screen,
i.e., <STRONG>curscr</STRONG>, <STRONG>newscr</STRONG>, or <STRONG>stdscr</STRONG>.
<STRONG>o</STRONG> <STRONG>set_term</STRONG> returns no error.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
These functions were described in X/Open Curses, Issue 4. As of 2015,
the current document is X/Open Curses, Issue 7.
</PRE><H3><a name="h3-Differences">Differences</a></H3><PRE>
X/Open Curses specifies that portable applications must not call
<STRONG>initscr</STRONG> more than once:
<STRONG>o</STRONG> The portable way to use <STRONG>initscr</STRONG> is once only, using <STRONG><A HREF="curs_refresh.3x.html">refresh(3x)</A></STRONG> to
restore the screen after <STRONG>endwin</STRONG>.
<STRONG>o</STRONG> This implementation allows using <STRONG>initscr</STRONG> after <STRONG>endwin</STRONG>.
Old versions of curses, e.g., BSD 4.4, would return a null pointer from
<STRONG>initscr</STRONG> when an error is detected, rather than exiting. It is safe but
redundant to check the return value of <STRONG>initscr</STRONG> in X/Open Curses.
Calling <STRONG>endwin</STRONG> does not dispose of the memory allocated in <STRONG>initscr</STRONG> or
<STRONG>newterm</STRONG>. Deleting a <EM>SCREEN</EM> provides a way to do this:
<STRONG>o</STRONG> X/Open Curses does not say what happens to <EM>WINDOW</EM>s when <STRONG>delscreen</STRONG>
"frees storage associated with the <EM>SCREEN</EM>" nor does the SVr4
documentation help, adding that it should be called after <STRONG>endwin</STRONG> if
a <EM>SCREEN</EM> is no longer needed.
<STRONG>o</STRONG> However, <EM>WINDOW</EM>s are implicitly associated with a <EM>SCREEN</EM>. so that
it is reasonable to expect <STRONG>delscreen</STRONG> to deal with these.
<STRONG>o</STRONG> SVr4 curses deletes the standard <EM>WINDOW</EM> structures <STRONG>stdscr</STRONG> and
<STRONG>curscr</STRONG> as well as a work area <STRONG>newscr</STRONG>. SVr4 curses ignores other
windows.
<STRONG>o</STRONG> Since version 4.0 (1996), <EM>ncurses</EM> has maintained a list of all
windows for each screen, using that information to delete those
windows when <STRONG>delscreen</STRONG> is called.
<STRONG>o</STRONG> NetBSD copied this feature of <EM>ncurses</EM> in 2001. PDCurses follows
the SVr4 model, deleting only the standard <EM>WINDOW</EM> structures.
</PRE><H3><a name="h3-High-level-versus-Low-level">High-level versus Low-level</a></H3><PRE>
Different implementations may disagree regarding the level of some
functions. For example, <EM>SCREEN</EM> (returned by <STRONG>newterm</STRONG>) and <EM>TERMINAL</EM>
(returned by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>) hold file descriptors for the output
stream. If an application switches screens using <STRONG>set_term</STRONG>, or switches
terminals using <STRONG><A HREF="curs_terminfo.3x.html">set_curterm(3x)</A></STRONG>, applications which use the output file
descriptor can have different behavior depending on which structure
holds the corresponding descriptor.
For example
<STRONG>o</STRONG> NetBSD's <STRONG><A HREF="curs_termattrs.3x.html">baudrate(3x)</A></STRONG> function uses the descriptor in <EM>TERMINAL</EM>.
<EM>ncurses</EM> and SVr4 use the descriptor in <EM>SCREEN</EM>.
<STRONG>o</STRONG> NetBSD and <EM>ncurses</EM> use the descriptor in <EM>TERMINAL</EM> for terminal I/O
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
uses the descriptor in <EM>SCREEN</EM>.
<STRONG>Unset</STRONG> <EM>TERM</EM> <STRONG>Variable</STRONG>
If the <EM>TERM</EM> variable is missing or empty, <STRONG>initscr</STRONG> uses the value
"unknown", which normally corresponds to a terminal entry with the
<EM>generic</EM> (<EM>gn</EM>) capability. Generic entries are detected by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>
and cannot be used for full-screen operation. Other implementations
may handle a missing/empty <EM>TERM</EM> variable differently.
</PRE><H3><a name="h3-Signal-Handlers">Signal Handlers</a></H3><PRE>
Quoting from 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 <EM>initscr</EM> 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., <STRONG>initscr</STRONG> or <STRONG>newterm</STRONG>. Applications which must handle these signals
should set up the corresponding handlers <EM>after</EM> initializing the
library:
<STRONG>SIGINT</STRONG>
The handler <EM>attempts</EM> to clean up the screen on exit. Although it
<EM>usually</EM> works as expected, there are limitations:
<STRONG>o</STRONG> Walking the <EM>SCREEN</EM> list is unsafe, since all list management
is done without any signal blocking.
<STRONG>o</STRONG> On systems which have <STRONG>REENTRANT</STRONG> turned on, <STRONG>set_term</STRONG> uses
functions which could deadlock or misbehave in other ways.
<STRONG>o</STRONG> <STRONG>endwin</STRONG> calls other functions, many of which use <STRONG>stdio(3)</STRONG> or
other library functions which are clearly unsafe.
<STRONG>SIGTERM</STRONG>
This uses the same handler as <STRONG>SIGINT</STRONG>, with the same limitations.
It is not mentioned in X/Open Curses, but is more suitable for
this purpose than <STRONG>SIGQUIT</STRONG> (which is used in debugging).
<STRONG>SIGTSTP</STRONG>
This handles the <EM>stop</EM> signal, used in job control. When resuming
the process, this implementation discards pending input with
<STRONG><A HREF="curs_util.3x.html">flushinp(3x)</A></STRONG>, and repaints the screen assuming that it has been
completely altered. It also updates the saved terminal modes with
<STRONG><A HREF="curs_kernel.3x.html">def_shell_mode(3x)</A></STRONG>.
<STRONG>SIGWINCH</STRONG>
This handles the window-size changes which were ignored in the
standardization efforts. The handler sets a (signal-safe)
variable which is later tested in <STRONG><A HREF="curs_getch.3x.html">wgetch(3x)</A></STRONG>. If <STRONG>keypad</STRONG> has been
enabled for the corresponding window, <STRONG>wgetch</STRONG> returns the key
symbol <STRONG>KEY_RESIZE</STRONG>. At the same time, <STRONG>wgetch</STRONG> calls <STRONG>resizeterm</STRONG> to
adjust the standard screen <STRONG>stdscr</STRONG>, and update other data such as
<STRONG>LINES</STRONG> and <STRONG>COLS</STRONG>.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<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><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>
ncurses 6.5 2024-04-20 <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-initscr">initscr</a></li>
<li><a href="#h3-newterm">newterm</a></li>
<li><a href="#h3-endwin">endwin</a></li>
<li><a href="#h3-isendwin">isendwin</a></li>
<li><a href="#h3-set_term">set_term</a></li>
<li><a href="#h3-delscreen">delscreen</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a>
<ul>
<li><a href="#h3-Differences">Differences</a></li>
<li><a href="#h3-High-level-versus-Low-level">High-level versus Low-level</a></li>
<li><a href="#h3-Signal-Handlers">Signal Handlers</a></li>
</ul>
</li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
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