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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | HISTORY | SEE ALSO | COLOPHON |
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curs_initscr(3X) Library calls curs_initscr(3X)
initscr, newterm, endwin, isendwin, set_term, delscreen -
initialize, manipulate, or tear down curses terminal interface
#include <curses.h>
WINDOW * initscr(void);
int endwin(void);
bool isendwin(void);
SCREEN * newterm(const char * type, FILE * outf, FILE * inf);
SCREEN * set_term(SCREEN * new);
void delscreen(SCREEN * sp);
initscr
initscr determines the terminal type and initializes the library's
SCREEN, WINDOW, and other data structures. It is normally the
first curses function call a program performs. However, an
application with unusual needs might employ a few other curses
functions beforehand:
• slk_init(3X) to set up soft-label keys;
• filter(3X) if the program is designed to operate in a process
pipeline;
• ripoffline(3X) to reserve up to five lines at the top and/or
bottom of the screen from management by stdscr, the standard
curses window; and
• use_env(3X) and/or use_tioctl(3X) to configure use of the
process environment and operating system's terminal driver,
respectively, when determining the dimensions of the terminal
display.
Further, a curses program might call newterm prior to or instead
of initscr in two specialized cases described in its subsection
below.
initscr causes the first refresh(3X) call to clear the screen. If
errors occur, initscr writes an appropriate diagnostic message to
the standard error stream and exits; otherwise, it returns a
pointer to stdscr.
newterm
An application that manages multiple terminals should call newterm
once for each such device instead of initscr. newterm's arguments
are
• the type of the associated terminal, or a null pointer to use
the TERM environment variable;
• an output stream outf connected to the terminal; and
• an input stream inf connected to the terminal.
newterm returns a variable of pointer-to-SCREEN type, which should
be saved for later use with set_term and delscreen.
newterm passes the file descriptor of the output stream to the
terminfo function setupterm(3X), which returns a pointer to a
TERMINAL structure that newterm stores in the SCREEN it returns to
the application.
An application that needs to inspect a terminal type's
capabilities, so that it can continue to run in a line-oriented
mode if the terminal type does not support capabilities the
application demands, would also use newterm. If at most one
terminal connection is needed, the programmer could perform such a
capability test, decide the mode in which to operate, then call
delscreen on the pointer returned by newterm, and proceed with
either initscr or a non-curses interface.
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 the application
or temporarily suspending curses's management of the terminal.
endwin:
• (if start_color(3X) has been called) resets the terminal's
foreground and background colors to correspond with those of
color pair 0 (the default pair),
• moves the cursor to the lower left-hand corner of the screen,
• (if start_color(3X) has been called) restores the default
color pair,
• clears the line,
• sets the cursor to normal visibility (see curs_set(3X)),
• if applicable, stops cursor-addressing mode using the
exit_ca_mode (rmcup) terminal capability, and
• restores terminal modes (see reset_shell_mode(3X)).
Calling refresh(3X) or doupdate(3X) after a temporary suspension
causes curses to resume managing the terminal.
isendwin
isendwin returns TRUE if wrefresh(3X) has not been called since
the most recent endwin call, and FALSE otherwise.
set_term
set_term re-orients the curses library's operations to another
terminal when the application has arranged to manage more than one
with newterm. set_term expects a SCREEN pointer previously
returned by newterm as an argument, and returns the previous one.
set_term is the only standard curses API function that manipulates
SCREEN pointers; all others affect only the current terminal (but
see curs_sp_funcs(3X)).
delscreen
delscreen frees the storage backing the supplied SCREEN pointer
argument. endwin does not, so that an application can resume
managing a terminal with curses after a (possibly conditional or
temporary) suspension; see curs_kernel(3X). Use delscreen after
endwin when the application has no more need of a terminal device
but will not soon exit.
delscreen returns no value. endwin returns OK on success and ERR
on failure. isendwin returns TRUE or FALSE as described above.
In ncurses,
• endwin returns ERR if
• the terminal was not initialized,
• it is called more than once without updating the screen,
or
• its call of reset_shell_mode(3X) returns ERR; and
• newterm returns ERR if it cannot allocate storage for the
SCREEN structure or the WINDOW structures automatically
associated with it: curscr, newscr, and stdscr.
Functions that return pointers return null pointers on error. In
ncurses, set_term does not fail, and initscr exits the application
if it does not operate successfully.
ncurses establishes signal handlers when a function that
initializes a SCREEN, either initscr or newterm, is first called.
Applications that wish to handle the following signals themselves
should set up their corresponding handlers after initializing the
screen.
SIGINT ncurses's handler attempts to clean up 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.
• When an application has been built with the _REENTRANT
macro defined (and corresponding system support),
set_term uses functions that could deadlock or
misbehave in other ways.
• endwin calls other functions, many of which use
stdio(3) or other library functions that are clearly
unsafe.
SIGTERM
ncurses uses the same handler as for 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
ncurses's handler manages the terminal-generated stop
signal, used in job control. When resuming the process,
ncurses discards pending input with flushinp(3X) and
repaints the screen, assuming that it has been completely
altered. It also updates the saved terminal modes with
def_shell_mode(3X).
SIGWINCH
ncurses handles changes to the terminal's window size, a
phenomenon ignored in standardization efforts. It sets a
(signal-safe) variable that is later tested by wgetch(3X)
and wget_wch(3X).
• wgetch returns the key code KEY_RESIZE.
• wget_wch returns KEY_CODE_YES and sets its wch
parameter to KEY_RESIZE.
At the same time, ncurses calls resizeterm(3X) to adjust
the standard screen stdscr and update global variables such
as LINES and COLS.
X/Open Curses Issue 4 describes these functions. It specifies no
error conditions for them.
Differences
X/Open Curses specifies that portable applications must not call
initscr more than once.
• The portable way to use initscr is once only, using refresh to
restore the screen after endwin.
• ncurses permits use of initscr after endwin.
initscr in BSD, from its inception (1980) through the Net/2
release (1991) returned ERR cast to a WINDOW pointer when
detecting an error. 4.4BSD (1995) instead returned a null
pointer. Neither exited the application. It is safe but
redundant to check the return value of initscr in X/Open Curses.
Calling endwin does not dispose of the memory allocated by initscr
or newterm. Deleting a SCREEN provides a way to do this.
• X/Open Curses does not say what happens to WINDOWs when
delscreen “frees storage associated with the SCREEN” nor does
the SVr4 documentation help, adding that it should be called
after endwin if a SCREEN is no longer needed.
• However, every WINDOW is implicitly associated with a SCREEN,
so it is reasonable to expect delscreen to dispose of them.
• SVr4 deletes the standard WINDOW structures stdscr and curscr
as well as a work area newscr. It ignores other windows.
• Since version 4.0 (1996), ncurses has maintained a list of all
windows for each screen, using that information to delete
those windows when delscreen is called.
• NetBSD copied this feature of ncurses in 2001. PDCurses
follows the SVr4 model, deleting only the standard WINDOW
structures and newscr.
High-level versus Low-level Functions
Implementations disagree regarding the level of abstraction
applicable to a function or property. For example, SCREEN
(returned by newterm) and TERMINAL (returned by setupterm(3X))
hold file descriptors for the output stream. If an application
switches screens using set_term, or switches terminals using
set_curterm(3X), applications using the output file descriptor can
behave differently depending on the structure holding the
corresponding descriptor.
• NetBSD's baudrate function uses the descriptor in TERMINAL.
ncurses and SVr4 use the descriptor in SCREEN.
• NetBSD and ncurses use the descriptor in TERMINAL for terminal
I/O modes, e.g., def_shell_mode(3X), def_prog_mode(3X). SVr4
uses the descriptor in SCREEN.
Unset TERM Environment Variable
If the TERM variable is not set in the environment or has an empty
value, initscr uses the value “unknown”, which normally
corresponds to a terminal entry with the generic (gn) capability.
Generic entries are detected by setupterm(3X) and cannot be used
for full-screen operation. Other implementations may handle a
missing or empty TERM variable differently.
Signal Handlers
Quoting 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 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...
Section “NOTES” above discusses ncurses's signal handlers.
4BSD (1980) introduced initscr and endwin.
SVr2 (1984) added newterm and set_term.
SVr3.1 (1987) supplied delscreen and isendwin.
curses(3X), curs_kernel(3X), curs_refresh(3X), curs_slk(3X),
curs_terminfo(3X), curs_util(3X), curs_variables(3X)
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://invisible-island.net/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to bug-ncurses@gnu.org.
This page was obtained from the tarball ncurses-6.6.tar.gz fetched
from ⟨https://ftp.gnu.org/gnu/ncurses/⟩ on 2026-01-16. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
ncurses @NCURSES_MAJOR@.@NCU... 2025-08-23 curs_initscr(3X)
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HTML rendering created 2026-01-16 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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