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Date: Tue, 28 Jul 2009 13:00:09 +0200
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Subject: 1.7.0: read() blocking with VMIN = VTIME = 0
From: =?ISO-8859-1?Q?daniel_=E5kerud?= <daniel DOT akerud AT gmail DOT com>
To: cygwin AT cygwin DOT com
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Hello!

With my example program below the read() is blocking even though
canonical input is set and VMIN = VTIME = 0.
It is supposed to act in a non-blocking way.

Does not work on:
CYGWIN_NT-5.0 1.7.0(0.212/5/3) 2009-07-24 09:59

Works on:
Linux version 2.6.28-13-generic (buildd AT vernadsky) (gcc version 4.3.3
(Ubuntu 4.3.3-5ubuntu4) ) #45-Ubuntu SMP Tue Jun 30 19:49:51 UTC 2009

Example program:

#include <stdio.h>
#include <unistd.h>
#include <termios.h>

int main() {
char c = 0;
struct termios term, term_orig;

if(tcgetattr(0, &term_orig)) {
printf("tcgetattr failed\n");
return 2;
}

term = term_orig;

term.c_lflag &= ~ICANON;
term.c_lflag |= ECHO;
term.c_cc[VMIN] = 0;
term.c_cc[VTIME] = 0;

if (tcsetattr(0, TCSANOW, &term)) {
printf("tcsetattr failed\n");
return 2;
}

printf("Calling read (blocks here on cygwin)\n");
fflush(stdout);

read(0, &c, 1);

printf("Back from read\n");

tcsetattr(0, TCSANOW, &term_orig);

return 0;
}

Is this supported in Cygwin? The only work around I know for now is to
do a select() before read()ing.

Best Regards,
Daniel

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