drk@athena.mit.edu (David R Kohr) (06/07/90)
I'm having a problem with the System V curses(3v) provided with Sun/OS
4.0.3. In particular, the nodelay() function, when given the argument
TRUE to turn off waiting for a keypress (so that mvgetch() becomes
non-blocking), seems simply not to work as advertised.
The following program is supposed to read a character from the terminal,
then display the character, number of repetitions through the loop, and
number of times no character was present to be read. It stops when 'q' is
pressed.
The program works fine when the call "nodelay(stdscr, FALSE);" is used:
mvgetch() waits for a keypress, as it should. But the call
"nodelay(stdscr, TRUE);" causes funny things to happen: a lot of the
repetitions through the loop aren't displayed, and when you first press a
character, the program "hangs" (no more displays at all), but it's really
still going through the loop, since if you stop the process with ^Z, you
get an updated display showing a higher number of repetitions than before.
Also, even if you do press 'q', the program can't be stopped unless you
kill it with ^C.
The halfdelay() function also doesn't work properly: if I substitute
"halfdelay(n);" for the nodelay() call, where n is anything between 1 and
255, mvgetch() still blocks (just like with "nodelay(stdscr, TRUE);"),
rather than using a timeout like it's supposed to.
I compiled the program with /usr/5bin/cc, so I think all the right headers
and libraries were used.
Here's the program:
---------------
#include <curses.h>
/*
Main function: repeatedly read character, displaying character read,
iteration number, and number of instances of no character present, at
end of each iteration. If character is 'q', end loop.
*/
void main()
{
int lastc = 0, /* Last char read from keyboard */
reps = 0, /* Repetitions of loop */
errs = 0; /* Occurences of ERR */
initscr();
cbreak();
noecho();
nodelay(stdscr, TRUE); /* Here's the call. */
while (lastc != 'q') {
if ((lastc = mvgetch(1, 1)) == ERR)
errs++;
mvprintw(2, 1, "Last character: %x ('%c')", lastc,
lastc & 0xFF);
mvprintw(3, 1, "Repetition number: %d", ++reps);
mvprintw(4, 1, "Occurrences of ERR: %d", errs);
refresh();
}
endwin();
}
If anyone can show me how to get this to work, I'd be much obliged.
Otherwise, if someone could explain to me how to do a non-blocking test
for a keypress (i.e., mvgetch() in nodelay(stdscr, TRUE) mode) using the
Berkeley curses(3x) package supplied with Sun/OS, that would probably
solve my problem also.
Thanks in advance,
David R. Kohr M.I.T. Lincoln Laboratory Group 45 ("Radars 'R' Us")
email: DRK@ATHENA.MIT.EDU (preferred) or KOHR@LL.LL.MIT.EDU
phone: (617)981-0775 (work) or (617)527-3908 (home)drk@athena.mit.edu (David R Kohr) (06/09/90)
In article <1990Jun8.002108.11536@athena.mit.edu> drk@athena.mit.edu (David R Kohr) writes: >I'm having a problem with the System V curses(3v) provided with >Sun/OS 4.0.3. I got the following reply from Carl Smith at Sun in response to a cross-posting of this article to comp.sys.sun: | From: cs@Eng.Sun.COM (Carl Smith) | Subject: Re: Problem with nodelay() in curses(3v) in Sun/OS 4.0.3. | | I discovered the same thing myself about a year ago and filed a bug on it. | It's bug #1012523, and it's fixed in SunOS 4.1. Here's the public summary | from that bug report: | | The curses library function wgetch fails when the window is put in | no delay mode (via nodelay(win, TRUE)). Characters in the tty input | queue are not read, and the return value of the function is incorrect. So I now know that the Sun/OS 4.0.3 nodelay() and halfdelay() System V curses(3v) routines definitely do *not* work properly. Now if someone could tell me how to achieve the same functionality as nodelay() by some other means (perhaps a non-blocking select(2) on the terminal device), that would completely solve my problem. David R. Kohr M.I.T. Lincoln Laboratory Group 45 ("Radars 'R' Us") email: DRK@ATHENA.MIT.EDU (preferred) or KOHR@LL.LL.MIT.EDU phone: (617)981-0775 (work) or (617)527-3908 (home)