man/curs_getstr.3x

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.\" $Id: curs_getstr.3x,v 1.58 2024/04/20 19:18:18 tom Exp $
.TH curs_getstr 3X 2024-04-20 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
.ie \n(.g \{\
.ds `` \(lq
.ds '' \(rq
.\}
.el \{\
.ie t .ds `` ``
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.
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.SH NAME
\fB\%getstr\fP,
\fB\%getnstr\fP,
\fB\%wgetstr\fP,
\fB\%wgetnstr\fP,
\fB\%mvgetstr\fP,
\fB\%mvgetnstr\fP,
\fB\%mvwgetstr\fP,
\fB\%mvwgetnstr\fP \-
accept character strings from \fIcurses\fR terminal keyboard
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fBint getstr(char *\fIstr\fP);
\fBint getnstr(char *\fIstr\fP, int \fIn\fP);
\fBint wgetstr(WINDOW *\fIwin\fP, char *\fIstr\fP);
\fBint wgetnstr(WINDOW *\fIwin\fP, char *\fIstr\fP, int \fIn\fP);
.PP
\fBint mvgetstr(int \fIy\fP, int \fIx\fP, char *\fIstr\fP);
\fBint mvwgetstr(WINDOW *\fIwin\fP, int \fIy\fP, int \fIx\fP, char *\fIstr\fP);
\fBint mvgetnstr(int \fIy\fP, int \fIx\fP, char *\fIstr\fP, int \fIn\fP);
\fBint mvwgetnstr(WINDOW *\fIwin\fP, int \fIy\fP, int \fIx\fP, char *\fIstr\fP, int \fIn\fP);
.fi
.SH DESCRIPTION
The function
\fBwgetnstr\fP
is equivalent to a series of calls to
\fBwgetch\fP(3X),
until a newline or carriage return terminates the series:
.bP
The terminating character is not included in the returned string.
.bP
In all instances, the end of the string is terminated
by a NUL.
.bP
The function stores the result in the area pointed to
by the \fIstr\fP parameter.
.bP
The function reads at most \fIn\fP characters,
thus preventing a possible overflow of the input buffer.
.IP
Any attempt to enter more characters
(other than the terminating newline or carriage return)
causes a beep.
.IP
Function keys also cause a beep and are ignored.
.PP
The user's \fIerase\fP and \fIkill\fP characters are interpreted:
.bP
The \fIerase\fP character (e.g., \fB^H\fP) erases the character
at the end of the buffer, moving the cursor to the left.
.IP
If \fIkeypad\fP mode is on for the window,
\fBKEY_LEFT\fP and \fBKEY_BACKSPACE\fP
are both considered equivalent to the user's \fIerase\fP character.
.bP
The \fIkill\fP character (e.g., \fB^U\fP) erases the entire buffer,
leaving the cursor at the beginning of the buffer.
.PP
Characters input are echoed only if \fBecho\fP is currently on.
In that case,
backspace is echoed as deletion of the previous character
(typically a left motion).
.PP
The
\fBgetnstr\fP,
\fBmvgetnstr\fP,
\fBmvwgetnstr\fP, and
\fBwgetnstr\fP
functions are identical
to the
\fBgetstr\fP,
\fBmvgetstr\fP,
\fBmvwgetstr\fP, and
\fBwgetstr\fP
functions, respectively,
except that the
\fB*n*\fP
versions read at most
\fIn\fP
characters, letting the application prevent overflow of the
input buffer.
.SH RETURN VALUE
All of these functions return the integer \fBOK\fP upon successful completion.
(SVr4 specifies only \*(``an integer value other than \fBERR\fP\*('')
If unsuccessful, they return \fBERR\fP.
.PP
X/Open defines no error conditions.
.PP
In this implementation,
these functions return an error
.bP
if the window pointer is null,
.bP
if its timeout expires without having any data, or
.bP
if the associated call to
\fBwgetch\fP
failed.
.PP
This implementation provides an extension as well.
If a \fBSIGWINCH\fP interrupts the function, it will return \fBKEY_RESIZE\fP
rather than \fBOK\fP or \fBERR\fP.
.PP
Functions prefixed with \*(``mv\*('' first perform cursor movement and
fail if the position
.RI ( y ,
.IR x )
is outside the window boundaries.
.SH NOTES
Any of these functions other than
\fBwgetnstr\fP
may be macros.
.PP
Using
\fBgetstr\fP,
\fBmvgetstr\fP,
\fBmvwgetstr\fP, or
\fBwgetstr\fP
to read a line that
overflows the array pointed to by
\fBstr\fP
causes undefined
results.
The use of
\fBgetnstr\fP,
\fBmvgetnstr\fP,
\fBmvwgetnstr\fP, or
\fBwgetnstr\fP,
respectively, is recommended.
.SH PORTABILITY
These functions are described in The Single Unix Specification, Version 2.
No error conditions are defined.
.PP
This implementation returns \fBERR\fP if the window pointer is null,
or if the lower-level \fBwgetch\fP(3X) call returns an \fBERR\fP.
.PP
SVr3 and early SVr4 curses implementations did not reject function keys;
the SVr4.0 documentation claimed that \*(``special keys\*(''
(such as function keys,
\*(``home\*('' key,
\*(``clear\*('' key,
\fIetc\fP.) are \*(``interpreted\*('',
without giving details.
It lied.
In fact, the \*(``character\*('' value appended to the
string by those implementations was predictable but not useful
(being, in fact, the low-order eight bits of the key's KEY_ value).
.PP
The functions \fBgetnstr\fP, \fBmvgetnstr\fP, and \fBmvwgetnstr\fP 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 count it, some do not:
.bP
\fI\%ncurses\fP 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
\fI\%ncurses\fP (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
\fI\%ncurses\fP 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,
\fI\%ncurses\fP uses the POSIX value for \fBLINE_MAX\fP (a 2048 byte limit).
In either case, it reserves a byte for the terminating NUL.
.PP
Although \fBgetnstr\fP is equivalent to a series of calls to \fBgetch\fP,
it also makes changes to the curses modes to allow simple editing of
the input buffer:
.bP
\fBgetnstr\fP saves the current value of the \fBnl\fP, \fBecho\fP,
\fBraw\fP and \fBcbreak\fP modes, and sets
\fBnl\fP,
\fBnoecho\fP,
\fBnoraw\fP, and
\fBcbreak\fP.
.IP
\fBgetnstr\fP handles the echoing of characters,
rather than relying on the caller to set an appropriate mode.
.bP
It also obtains the \fIerase\fP and \fIkill\fP characters
from \fBerasechar\fP and \fBkillchar\fP, respectively.
.bP
On return, \fBgetnstr\fP restores the modes to their previous values.
.PP
Other implementations differ in their treatment of special characters:
.bP
While they may set the \fIecho\fP mode,
other implementations do not modify the \fIraw\fP mode,
They may take the \fIcbreak\fP
mode set by the caller into account when deciding whether to handle
echoing within \fBgetnstr\fP or as a side-effect of the \fBgetch\fP calls.
.bP
The original \fI\%ncurses\fP
(as \fIpcurses\fP in 1986)
set \fBnoraw\fP and \fBcbreak\fP when accepting input for \fBgetnstr\fP.
That may have been done to make function- and cursor-keys work;
it is not necessary with \fI\%ncurses\fP.
.IP
Since 1995,
\fI\%ncurses\fP has provided signal handlers for INTR and QUIT
(e.g., \fB^C\fP or \fB^\e\fP).
With the \fBnoraw\fP and \fBcbreak\fP settings,
those may catch a signal and stop the program,
where other implementations allow one to enter those characters in the buffer.
.bP
Starting in 2021
(\fI\%ncurses\fP 6.3),
\fBgetnstr\fP sets \fBraw\fP,
rather than \fBnoraw\fP and \fBcbreak\fP for better compatibility with
SVr4-curses, e.g., allowing one to enter a \fB^C\fP into the buffer.
.SH SEE ALSO
\fB\%curs_get_wstr\fP(3X) describes comparable functions of the
.I \%ncurses
library in its wide-character configuration
.RI ( \%ncursesw ).
.PP
\fB\%curses\fP(3X),
\fB\%curs_getch\fP(3X),
\fB\%curs_termattrs\fP(3X),
\fB\%curs_variables\fP(3X)