293 lines
10 KiB
Groff
293 lines
10 KiB
Groff
.\" $OpenBSD: curs_getstr.3,v 1.10 2023/10/17 09:52:08 nicm Exp $
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.\"
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.\"***************************************************************************
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.\" Copyright 2018-2022,2023 Thomas E. Dickey *
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.\" Copyright 1998-2010,2017 Free Software Foundation, Inc. *
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.\" *
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.\" Permission is hereby granted, free of charge, to any person obtaining a *
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.\" copy of this software and associated documentation files (the *
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.\" "Software"), to deal in the Software without restriction, including *
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.\" without limitation the rights to use, copy, modify, merge, publish, *
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.\" distribute, distribute with modifications, sublicense, and/or sell *
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.\" copies of the Software, and to permit persons to whom the Software is *
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.\" furnished to do so, subject to the following conditions: *
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.\" *
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.\" The above copyright notice and this permission notice shall be included *
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.\" in all copies or substantial portions of the Software. *
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.\" *
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.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
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.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
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.\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
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.\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
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.\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
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.\" THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
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.\" *
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.\" Except as contained in this notice, the name(s) of the above copyright *
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.\" holders shall not be used in advertising or otherwise to promote the *
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.\" sale, use or other dealings in this Software without prior written *
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.\" authorization. *
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.\"***************************************************************************
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.\"
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.\" $Id: curs_getstr.3,v 1.10 2023/10/17 09:52:08 nicm Exp $
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.TH curs_getstr 3 2023-08-05 "ncurses 6.4" "Library calls"
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.ie \n(.g .ds `` \(lq
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.el .ds `` ``
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.ie \n(.g .ds '' \(rq
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.el .ds '' ''
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.de bP
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.ie n .IP \(bu 4
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.el .IP \(bu 2
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..
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.na
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.hy 0
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.SH NAME
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\fBgetstr\fP,
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\fBgetnstr\fP,
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\fBwgetstr\fP,
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\fBwgetnstr\fP,
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\fBmvgetstr\fP,
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\fBmvgetnstr\fP,
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\fBmvwgetstr\fP,
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\fBmvwgetnstr\fP \- accept character strings from \fBcurses\fP terminal keyboard
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.ad
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.hy
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.SH SYNOPSIS
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\fB#include <curses.h>\fP
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.sp
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\fBint getstr(char *\fIstr\fB);\fR
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.br
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\fBint getnstr(char *\fIstr\fB, int \fIn\fB);\fR
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.br
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\fBint wgetstr(WINDOW *\fIwin\fB, char *\fIstr\fB);\fR
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.br
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\fBint wgetnstr(WINDOW *\fIwin\fB, char *\fIstr\fB, int \fIn\fB);\fR
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.sp
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\fBint mvgetstr(int \fIy\fB, int \fIx\fB, char *\fIstr\fB);\fR
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.br
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\fBint mvwgetstr(WINDOW *\fIwin\fB, int \fIy\fB, int \fIx\fB, char *\fIstr\fB);\fR
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.br
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\fBint mvgetnstr(int \fIy\fB, int \fIx\fB, char *\fIstr\fB, int \fIn\fB);\fR
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.br
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\fBint mvwgetnstr(WINDOW *\fIwin\fB, int \fIy\fB, int \fIx\fB, char *\fIstr\fB, int \fIn\fB);\fR
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.SH DESCRIPTION
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The function
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\fBwgetnstr\fP
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is equivalent to a series of calls to
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\fBwgetch\fP(3),
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until a newline or carriage return terminates the series:
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.bP
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The terminating character is not included in the returned string.
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.bP
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In all instances, the end of the string is terminated
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by a NUL.
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.bP
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The function stores the result in the area pointed to
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by the \fIstr\fP parameter.
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.bP
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The function reads at most \fIn\fP characters,
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thus preventing a possible overflow of the input buffer.
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.IP
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Any attempt to enter more characters
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(other than the terminating newline or carriage return)
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causes a beep.
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.IP
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Function keys also cause a beep and are ignored.
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.PP
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The user's \fIerase\fP and \fIkill\fP characters are interpreted:
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.bP
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The \fIerase\fP character (e.g., \fB^H\fP) erases the character
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at the end of the buffer, moving the cursor to the left.
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.IP
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If \fIkeypad\fP mode is on for the window,
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\fBKEY_LEFT\fP and \fBKEY_BACKSPACE\fP
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are both considered equivalent to the user's \fIerase\fP character.
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.bP
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The \fIkill\fP character (e.g., \fB^U\fP) erases the entire buffer,
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leaving the cursor at the beginning of the buffer.
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.PP
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Characters input are echoed only if \fBecho\fP is currently on.
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In that case,
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backspace is echoed as deletion of the previous character
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(typically a left motion).
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.PP
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The
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\fBgetnstr\fP,
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\fBmvgetnstr\fP,
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\fBmvwgetnstr\fP, and
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\fBwgetnstr\fP
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functions are identical
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to the
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\fBgetstr\fP,
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\fBmvgetstr\fP,
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\fBmvwgetstr\fP, and
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\fBwgetstr\fP
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functions, respectively,
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except that the
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\fB*n*\fP
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versions read at most
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\fIn\fP
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characters, letting the application prevent overflow of the
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input buffer.
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.SH NOTES
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Any of these functions other than
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\fBwgetnstr\fP
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may be macros.
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.PP
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Using
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\fBgetstr\fP,
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\fBmvgetstr\fP,
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\fBmvwgetstr\fP, or
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\fBwgetstr\fP
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to read a line that
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overflows the array pointed to by
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\fBstr\fP
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causes undefined
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results.
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The use of
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\fBgetnstr\fP,
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\fBmvgetnstr\fP,
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\fBmvwgetnstr\fP, or
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\fBwgetnstr\fP,
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respectively, is recommended.
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.SH RETURN VALUE
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All of these functions return the integer \fBOK\fP upon successful completion.
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(SVr4 specifies only \*(``an integer value other than \fBERR\fP\*('')
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If unsuccessful, they return \fBERR\fP.
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.PP
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X/Open defines no error conditions.
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.PP
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In this implementation,
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these functions return an error
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.bP
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if the window pointer is null,
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.bP
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if its timeout expires without having any data, or
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.bP
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if the associated call to
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\fBwgetch\fP
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failed.
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.PP
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This implementation provides an extension as well.
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If a \fBSIGWINCH\fP interrupts the function, it will return \fBKEY_RESIZE\fP
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rather than \fBOK\fP or \fBERR\fP.
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.PP
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Functions with a \*(``mv\*('' prefix first perform a cursor movement using
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\fBwmove\fP, and return an error if the position is outside the window,
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or if the window pointer is null.
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.SH PORTABILITY
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These functions are described in The Single Unix Specification, Version 2.
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No error conditions are defined.
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.PP
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This implementation returns \fBERR\fP if the window pointer is null,
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or if the lower-level \fBwgetch\fP(3) call returns an \fBERR\fP.
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.PP
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SVr3 and early SVr4 curses implementations did not reject function keys;
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the SVr4.0 documentation claimed that \*(``special keys\*(''
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(such as function keys,
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\*(``home\*('' key,
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\*(``clear\*('' key,
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\fIetc\fP.) are \*(``interpreted\*('',
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without giving details.
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It lied.
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In fact, the \*(``character\*('' value appended to the
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string by those implementations was predictable but not useful
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(being, in fact, the low-order eight bits of the key's KEY_ value).
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.PP
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The functions \fBgetnstr\fP, \fBmvgetnstr\fP, and \fBmvwgetnstr\fP were
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present but not documented in SVr4.
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.PP
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X/Open Curses, Issue 5 (2007) stated that these functions
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\*(``read at most \fIn\fP bytes\*(''
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but did not state whether the terminating NUL is counted in that limit.
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X/Open Curses, Issue 7 (2009) changed that to say they
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\*(``read at most \fIn\fP\-1 bytes\*(''
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to allow for the terminating NUL.
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As of 2018, some implementations count it, some do not:
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.bP
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ncurses 6.1 and PDCurses do not count the NUL in the given limit, while
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.bP
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Solaris SVr4 and NetBSD curses count the NUL as part of the limit.
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.bP
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Solaris xcurses provides both:
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its wide-character \fBwget_nstr\fP reserves a NUL,
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but its \fBwgetnstr\fP does not count the NUL consistently.
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.PP
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In SVr4 curses,
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a negative value of \fIn\fP tells \fBwgetnstr\fP to assume that the
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caller's buffer is large enough to hold the result,
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i.e., to act like \fBwgetstr\fP.
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X/Open Curses does not mention this
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(or anything related to negative or zero values of \fIn\fP),
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however most implementations
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use the feature, with different limits:
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.bP
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Solaris SVr4 curses and PDCurses limit the result to 255 bytes.
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Other Unix systems than Solaris are likely to use the same limit.
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.bP
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Solaris xcurses limits the result to \fBLINE_MAX\fP bytes.
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.bP
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NetBSD 7 assumes no particular limit for the result from \fBwgetstr\fP.
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However, it limits the \fBwgetnstr\fP parameter \fIn\fP to ensure
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that it is greater than zero.
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.IP
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A comment in NetBSD's source code states that this is specified in SUSv2.
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.bP
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ncurses (before 6.2) assumes no particular limit for the result
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from \fBwgetstr\fP, and treats the \fIn\fP parameter of \fBwgetnstr\fP
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like SVr4 curses.
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.bP
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ncurses 6.2 uses \fBLINE_MAX\fP,
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or a larger (system-dependent) value
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which the \fBsysconf\fP function may provide.
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If neither \fBLINE_MAX\fP or \fBsysconf\fP is available,
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ncurses uses the POSIX value for \fBLINE_MAX\fP (a 2048 byte limit).
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In either case, it reserves a byte for the terminating NUL.
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.PP
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Although \fBgetnstr\fP is equivalent to a series of calls to \fBgetch\fP,
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it also makes changes to the curses modes to allow simple editing of
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the input buffer:
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.bP
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\fBgetnstr\fP saves the current value of the \fBnl\fP, \fBecho\fP,
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\fBraw\fP and \fBcbreak\fP modes, and sets
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\fBnl\fP,
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\fBnoecho\fP,
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\fBnoraw\fP, and
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\fBcbreak\fP.
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.IP
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\fBgetnstr\fP handles the echoing of characters,
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rather than relying on the caller to set an appropriate mode.
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.bP
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It also obtains the \fIerase\fP and \fIkill\fP characters
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from \fBerasechar\fP and \fBkillchar\fP, respectively.
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.bP
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On return, \fBgetnstr\fP restores the modes to their previous values.
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.PP
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Other implementations differ in their treatment of special characters:
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.bP
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While they may set the \fIecho\fP mode,
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other implementations do not modify the \fIraw\fP mode,
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They may take the \fIcbreak\fP
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mode set by the caller into account when deciding whether to handle
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echoing within \fBgetnstr\fP or as a side-effect of the \fBgetch\fP calls.
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.bP
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The original ncurses (as \fIpcurses\fP in 1986) set \fBnoraw\fP and \fBcbreak\fP
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when accepting input for \fBgetnstr\fP.
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That may have been done to make function- and cursor-keys work;
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it is not necessary with ncurses.
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.IP
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Since 1995, ncurses has provided signal handlers for INTR and QUIT
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(e.g., \fB^C\fP or \fB^\\\fP).
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With the \fBnoraw\fP and \fBcbreak\fP settings,
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those may catch a signal and stop the program,
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where other implementations allow one to enter those characters in the buffer.
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.bP
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Starting in 2021 (ncurses 6.3), \fBgetnstr\fP sets \fBraw\fP,
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rather than \fBnoraw\fP and \fBcbreak\fP for better compatibility with
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SVr4-curses, e.g., allowing one to enter a \fB^C\fP into the buffer.
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.SH SEE ALSO
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\fBcurses\fP(3),
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\fBcurs_getch\fP(3),
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\fBcurs_termattrs\fP(3),
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\fBcurs_variables\fP(3).
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