1curs_initscr(3X) curs_initscr(3X)
2
6 initscr, newterm, endwin, isendwin, set_term, delscreen - curses screen
7 initialization and manipulation routines
8
10 #include <curses.h>
11 WINDOW *initscr(void);
13 int endwin(void);
14 bool isendwin(void);
16 SCREEN *newterm(const char *type, FILE *outfd, FILE *infd);
18 SCREEN *set_term(SCREEN *new);
19 void delscreen(SCREEN* sp);
20
22 initscr
23 initscr is normally the first curses routine to call when initializing
24 a program. A few special routines sometimes need to be called before
25 it; these are slk_init(3X), filter, ripoffline, use_env. For multiple-
26 terminal applications, newterm may be called before initscr.
27 The initscr code determines the terminal type and initializes all curs‐
29 es data structures. initscr also causes the first call to refresh(3X)
30 to clear the screen. If errors occur, initscr writes an appropriate
31 error message to standard error and exits; otherwise, a pointer is re‐
32 turned to stdscr.
33 newterm
35 A program that outputs to more than one terminal should use the newterm
36 routine for each terminal instead of initscr. A program that needs to
37 inspect capabilities, so it can continue to run in a line-oriented mode
38 if the terminal cannot support a screen-oriented program, would also
39 use newterm. The routine newterm should be called once for each termi‐
40 nal. It returns a variable of type SCREEN * which should be saved as a
41 reference to that terminal. newterm's arguments are
42 • the type of the terminal to be used in place of $TERM,
44 • a file pointer for output to the terminal, and
46 • another file pointer for input from the terminal
48 If the type parameter is NULL, $TERM will be used.
50 endwin
52 The program must also call endwin for each terminal being used before
53 exiting from curses. If newterm is called more than once for the same
54 terminal, the first terminal referred to must be the last one for which
55 endwin is called.
56 A program should always call endwin before exiting or escaping from
58 curses mode temporarily. This routine
59 • resets colors to correspond with the default color pair 0,
61 • moves the cursor to the lower left-hand corner of the screen,
63 • clears the remainder of the line so that it uses the default col‐
65 ors,
66 • sets the cursor to normal visibility (see curs_set(3X)),
68 • stops cursor-addressing mode using the exit_ca_mode terminal capa‐
70 bility,
71 • restores tty modes (see reset_shell_mode(3X)).
73 Calling refresh(3X) or doupdate(3X) after a temporary escape causes the
75 program to resume visual mode.
76 isendwin
78 The isendwin routine returns TRUE if endwin has been called without any
79 subsequent calls to wrefresh, and FALSE otherwise.
80 set_term
82 The set_term routine is used to switch between different terminals.
83 The screen reference new becomes the new current terminal. The previ‐
84 ous terminal is returned by the routine. This is the only routine
85 which manipulates SCREEN pointers; all other routines affect only the
86 current terminal.
87 delscreen
89 The delscreen routine frees storage associated with the SCREEN data
90 structure. The endwin routine does not do this, so delscreen should be
91 called after endwin if a particular SCREEN is no longer needed.
92
94 endwin returns the integer ERR upon failure and OK upon successful com‐
95 pletion.
96 Routines that return pointers always return NULL on error.
98 X/Open defines no error conditions. In this implementation
100 • endwin returns an error if the terminal was not initialized.
102 • newterm returns an error if it cannot allocate the data structures
104 for the screen, or for the top-level windows within the screen,
105 i.e., curscr, newscr, or stdscr.
106 • set_term returns no error.
108
110 These functions were described in the XSI Curses standard, Issue 4. As
111 of 2015, the current document is X/Open Curses, Issue 7.
112 Differences
114 X/Open specifies that portable applications must not call initscr more
115 than once:
116 • The portable way to use initscr is once only, using refresh (see
118 curs_refresh(3X)) to restore the screen after endwin.
119 • This implementation allows using initscr after endwin.
121 Old versions of curses, e.g., BSD 4.4, would return a null pointer from
123 initscr when an error is detected, rather than exiting. It is safe but
124 redundant to check the return value of initscr in XSI Curses.
125 Calling endwin does not dispose of the memory allocated in initscr or
127 newterm. Deleting a SCREEN provides a way to do this:
128 • X/Open Curses does not say what happens to WINDOWs when delscreen
130 “frees storage associated with the SCREEN” nor does the SVr4 docu‐
131 mentation help, adding that it should be called after endwin if a
132 SCREEN is no longer needed.
133 • However, WINDOWs are implicitly associated with a SCREEN. so that
135 it is reasonable to expect delscreen to deal with these.
136 • SVr4 curses deletes the standard WINDOW structures stdscr and
138 curscr as well as a work area newscr. SVr4 curses ignores other
139 windows.
140 • Since version 4.0 (1996), ncurses has maintained a list of all win‐
142 dows for each screen, using that information to delete those win‐
143 dows when delscreen is called.
144 • NetBSD copied this feature of ncurses in 2001. PDCurses follows
146 the SVr4 model, deleting only the standard WINDOW structures.
147 Unset TERM Variable
149 If the TERM variable is missing or empty, initscr uses the value “un‐
150 known”, which normally corresponds to a terminal entry with the generic
151 (gn) capability. Generic entries are detected by setupterm (see
152 curs_terminfo(3X)) and cannot be used for full-screen operation. Other
153 implementations may handle a missing/empty TERM variable differently.
154 Signal Handlers
156 Quoting from X/Open Curses, section 3.1.1:
157 Curses implementations may provide for special handling of the
159 SIGINT, SIGQUIT and SIGTSTP signals if their disposition is
160 SIG_DFL at the time initscr is called ...
161 Any special handling for these signals may remain in effect for
163 the life of the process or until the process changes the
164 disposition of the signal.
165 None of the Curses functions are required to be safe with respect
167 to signals ...
168 This implementation establishes signal handlers during initialization,
170 e.g., initscr or newterm. Applications which must handle these signals
171 should set up the corresponding handlers after initializing the li‐
172 brary:
173 SIGINT
175 The handler attempts to cleanup the screen on exit. Although it
176 usually works as expected, there are limitations:
177 • Walking the SCREEN list is unsafe, since all list management
179 is done without any signal blocking.
180 • On systems which have REENTRANT turned on, set_term uses func‐
182 tions which could deadlock or misbehave in other ways.
183 • endwin calls other functions, many of which use stdio or other
185 library functions which are clearly unsafe.
186 SIGTERM
188 This uses the same handler as SIGINT, with the same limitations.
189 It is not mentioned in X/Open Curses, but is more suitable for
190 this purpose than SIGQUIT (which is used in debugging).
191 SIGTSTP
193 This handles the stop signal, used in job control. When resuming
194 the process, this implementation discards pending input with
195 flushinput (see curs_util(3X)), and repaints the screen assuming
196 that it has been completely altered. It also updates the saved
197 terminal modes with def_shell_mode (see curs_kernel(3X)).
198 SIGWINCH
200 This handles the window-size changes which were ignored in the
201 standardization efforts. The handler sets a (signal-safe) vari‐
202 able which is later tested in wgetch (see curs_getch(3X)). If
203 keypad has been enabled for the corresponding window, wgetch re‐
204 turns the key symbol KEY_RESIZE. At the same time, wgetch calls
205 resizeterm to adjust the standard screen stdscr, and update other
206 data such as LINES and COLS.
207
209 curses(3X), curs_kernel(3X), curs_refresh(3X), curs_slk(3X), curs_ter‐
210 minfo(3X), curs_util(3X), curs_variables(3X).
211 curs_initscr(3X)