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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | COLOPHON |
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curs_getstr(3X) curs_getstr(3X)
getstr, getnstr, wgetstr, wgetnstr, mvgetstr, mvgetnstr,
mvwgetstr, mvwgetnstr - accept character strings from curses
terminal keyboard
#include <curses.h>
int getstr(char *str);
int getnstr(char *str, int n);
int wgetstr(WINDOW *win, char *str);
int wgetnstr(WINDOW *win, char *str, int n);
int mvgetstr(int y, int x, char *str);
int mvwgetstr(WINDOW *win, int y, int x, char *str);
int mvgetnstr(int y, int x, char *str, int n);
int mvwgetnstr(WINDOW *win, int y, int x, char *str, int n);
The function getstr is equivalent to a series of calls to getch,
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
str, followed by a NUL.
The getnstr function reads from the stdscr default window. The
other functions, such as wgetnstr, read from the window given as
a parameter.
getnstr reads at most n characters, thus preventing a possible
overflow of the input buffer. Any attempt to enter more charac‐
ters (other than the terminating newline or carriage return)
causes a beep. Function keys also cause a beep and are ignored.
The user's erase and kill characters are interpreted:
• The erase character (e.g., ^H) erases the character at the
end of the buffer, moving the cursor to the left.
If keypad mode is on for the window, KEY_LEFT and KEY_BACK‐
SPACE are both considered equivalent to the user's erase
character.
• The kill character (e.g., ^U) erases the entire buffer, leav‐
ing the cursor at the beginning of the buffer.
Characters input are echoed only if echo is currently on. In
that case, backspace is echoed as deletion of the previous char‐
acter (typically a left motion).
All routines return the integer ERR upon failure and an OK (SVr4
specifies only “an integer value other than ERR”) upon successful
completion.
X/Open defines no error conditions.
In this implementation, these functions return an error if the
window pointer is null, or if its timeout expires without having
any data.
This implementation provides an extension as well. If a SIGWINCH
interrupts the function, it will return KEY_RESIZE rather than OK
or ERR.
Functions with a “mv” prefix first perform a cursor movement us‐
ing wmove, and return an error if the position is outside the
window, or if the window pointer is null.
Note that getstr, mvgetstr, and mvwgetstr may be macros.
These functions are described in the XSI Curses standard, Issue
4. They read single-byte characters only. The standard does not
define any error conditions. This implementation returns ERR if
the window pointer is null, or if the lower-level wgetch(3X) call
returns an ERR.
SVr3 and early SVr4 curses implementations did not reject func‐
tion keys; the SVr4.0 documentation claimed that “special keys”
(such as function keys, “home” key, “clear” key, etc.) are “in‐
terpreted”, 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).
The functions getnstr, mvgetnstr, and mvwgetnstr were present but
not documented in SVr4.
X/Open Curses, Issue 5 (2007) stated that these functions “read
at most n 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 n-1 bytes” to allow for the termi‐
nating NUL. As of 2018, some implementations do, some do not
count it:
• ncurses 6.1 and PDCurses do not count the NUL in the given
limit, while
• Solaris SVr4 and NetBSD curses count the NUL as part of the
limit.
• Solaris xcurses provides both: its wide-character wget_nstr
reserves a NUL, but its wgetnstr does not count the NUL con‐
sistently.
In SVr4 curses, a negative value of n tells wgetnstr to assume
that the caller's buffer is large enough to hold the result,
i.e., to act like wgetstr. X/Open Curses does not mention this
(or anything related to negative or zero values of n), however
most implementations use the feature, with different limits:
• Solaris SVr4 curses and PDCurses limit the result to 255
bytes. Other Unix systems than Solaris are likely to use the
same limit.
• Solaris xcurses limits the result to LINE_MAX bytes.
• NetBSD 7 assumes no particular limit for the result from
wgetstr. However, it limits the wgetnstr parameter n to en‐
sure that it is greater than zero.
A comment in NetBSD's source code states that this is speci‐
fied in SUSv2.
• ncurses (before 6.2) assumes no particular limit for the re‐
sult from wgetstr, and treats the n parameter of wgetnstr
like SVr4 curses.
• ncurses 6.2 uses LINE_MAX, or a larger (system-dependent)
value which the sysconf function may provide. If neither
LINE_MAX or sysconf is available, ncurses uses the POSIX val‐
ue for LINE_MAX (a 2048 byte limit). In either case, it re‐
serves a byte for the terminating NUL.
Although getnstr is equivalent to a series of calls to getch, it
also makes changes to the curses modes to allow simple editing of
the input buffer:
• getnstr saves the current value of the nl, echo, raw and
cbreak modes, and sets nl, noecho, noraw, and cbreak.
getnstr handles the echoing of characters, rather than rely‐
ing on the caller to set an appropriate mode.
• It also obtains the erase and kill characters from erasechar
and killchar, respectively.
• On return, getnstr restores the modes to their previous val‐
ues.
Other implementations differ in their treatment of special char‐
acters:
• While they may set the echo mode, other implementations do
not modify the raw mode, They may take the cbreak mode set by
the caller into account when deciding whether to handle echo‐
ing within getnstr or as a side-effect of the getch calls.
• The original ncurses (as pcurses in 1986) set noraw and
cbreak when accepting input for getnstr. That may have been
done to make function- and cursor-keys work; it is not neces‐
sary with ncurses.
Since 1995, ncurses has provided signal handlers for INTR and
QUIT (e.g., ^C or ^\). With the noraw and cbreak settings,
those may catch a signal and stop the program, where other
implementations allow one to enter those characters in the
buffer.
• Starting in 2021 (ncurses 6.3), getnstr sets raw, rather than
noraw and cbreak for better compatibility with SVr4-curses,
e.g., allowing one to enter a ^C into the buffer.
curses(3X), curs_getch(3X), curs_termattrs(3X), curs_vari‐
ables(3X).
This page is part of the ncurses (new curses) project. Informa‐
tion about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have
a bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) 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
[email protected]
curs_getstr(3X)
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HTML rendering created 2024-06-26 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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