.\"***************************************************************************
-.\" Copyright (c) 1998-2010,2017 Free Software Foundation, Inc. *
+.\" Copyright 2018-2019,2020 Thomas E. Dickey *
+.\" Copyright 1998-2010,2017 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_getstr.3x,v 1.23 2017/11/21 00:45:48 tom Exp $
+.\" $Id: curs_getstr.3x,v 1.29 2020/02/02 23:34:34 tom Exp $
.TH curs_getstr 3X ""
.ie \n(.g .ds `` \(lq
.el .ds `` ``
.ie \n(.g .ds '' \(rq
.el .ds '' ''
+.de bP
+.ie n .IP \(bu 4
+.el .IP \(bu 2
+..
.na
.hy 0
.SH NAME
.SH DESCRIPTION
The function \fBgetstr\fR is equivalent to a series of calls to \fBgetch\fR,
until a newline or carriage return is received (the terminating character is
-not included in the returned string). The resulting value is placed in the
-area pointed to by the character pointer \fIstr\fR.
+not included in the returned string).
+.\" X/Open says also until EOf
+.\" X/Open says then an EOS is added to the result
+.\" X/Open doesn't mention n<0
+The resulting value is placed in the
+area pointed to by the character pointer \fIstr\fR,
+followed by a NUL.
.PP
\fBwgetnstr\fR reads at most \fIn\fR characters, thus preventing a possible
-overflow of the input buffer. Any attempt to enter more characters (other
-than the terminating newline or carriage return) causes a beep. Function
-keys also cause a beep and are ignored. The \fBgetnstr\fR function reads
+overflow of the input buffer.
+Any attempt to enter more characters (other
+than the terminating newline or carriage return) causes a beep.
+Function
+keys also cause a beep and are ignored.
+The \fBgetnstr\fR function reads
from the \fIstdscr\fR default window.
.PP
-The user's erase and kill characters are interpreted. If keypad
+The user's erase and kill characters are interpreted.
+If keypad
mode is on for the window, \fBKEY_LEFT\fR and \fBKEY_BACKSPACE\fR
are both considered equivalent to the user's kill character.
.PP
-Characters input are echoed only if \fBecho\fR is currently on. In that case,
+Characters input are echoed only if \fBecho\fR is currently on.
+In that case,
backspace is echoed as deletion of the previous character (typically a left
motion).
.SH RETURN VALUE
.PP
The functions \fBgetnstr\fR, \fBmvgetnstr\fR, and \fBmvwgetnstr\fR were
present but not documented in SVr4.
+.PP
+X/Open Curses, Issue 5 (2007) stated that these functions
+\*(``read at most \fIn\fP bytes\*(''
+but did not state whether the terminating NUL is counted in that limit.
+X/Open Curses, Issue 7 (2009) changed that to say they
+\*(``read at most \fIn\fP\-1 bytes\*(''
+to allow for the terminating NUL.
+As of 2018, some implementations do, some do not count it:
+.bP
+ncurses 6.1 and PDCurses do not count the NUL in the given limit, while
+.bP
+Solaris SVr4 and NetBSD curses count the NUL as part of the limit.
+.bP
+Solaris xcurses provides both:
+its wide-character \fBwget_nstr\fP reserves a NUL,
+but its \fBwgetnstr\fP does not count the NUL consistently.
+.PP
+In SVr4 curses,
+a negative value of \fIn\fP tells \fBwgetnstr\fP to assume that the
+caller's buffer is large enough to hold the result,
+i.e., to act like \fBwgetstr\fP.
+X/Open Curses does not mention this
+(or anything related to negative or zero values of \fIn\fP),
+however most implementations
+use the feature, with different limits:
+.bP
+Solaris SVr4 curses and PDCurses limit the result to 255 bytes.
+Other Unix systems than Solaris are likely to use the same limit.
+.bP
+Solaris xcurses limits the result to \fBLINE_MAX\fP bytes.
+.bP
+NetBSD 7 assumes no particular limit for the result from \fBwgetstr\fP.
+However, it limits the \fBwgetnstr\fP parameter \fIn\fP to ensure
+that it is greater than zero.
+.IP
+A comment in NetBSD's source code states that this is specified in SUSv2.
+.bP
+ncurses (before 6.2) assumes no particular limit for the result
+from \fBwgetstr\fP, and treats the \fIn\fP parameter of \fBwgetnstr\fP
+like SVr4 curses.
+.bP
+ncurses 6.2 uses \fBLINE_MAX\fP,
+or a larger (system-dependent) value
+which the \fBsysconf\fP function may provide.
+If neither \fBLINE_MAX\fP or \fBsysconf\fP is available,
+ncurses uses the POSIX value for \fBLINE_MAX\fP (a 2048 byte limit).
+In either case, it reserves a byte for the terminating NUL.
.SH SEE ALSO
\fBcurses\fR(3X),
\fBcurs_getch\fR(3X),
projects / ncurses.git / blobdiff