Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
The very first thing you should do is look into getting the Term::ReadKey extension from CPAN. It now even has limited support for closed, proprietary (read: not open systems, not POSIX, not Unix, etc) systems.
You should also check out the Frequently Asked Questions list in comp.unix.* for things like this: the answer is essentially the same. It's very system dependent. Here's one solution that works on BSD systems:
sub key_ready { my($rin, $nfd); vec($rin, fileno(STDIN), 1) = 1; return $nfd = select($rin,undef,undef,0); }
If you want to find out how many characters are waiting, there's also the FIONREAD ioctl call to be looked at.
The h2ph tool that comes with Perl tries to convert C include files to Perl code, which can be required. FIONREAD ends up defined as a function in the sys/ioctl.ph file:
require 'sys/ioctl.ph';
$size = pack("L", 0); ioctl(FH, FIONREAD(), $size) or die "Couldn't call ioctl: $!\n"; $size = unpack("L", $size);
If h2ph wasn't installed or doesn't work for you, you can grep the include files by hand:
% grep FIONREAD /usr/include/*/* /usr/include/asm/ioctls.h:#define FIONREAD 0x541B
Or write a small C program using the editor of champions:
% cat > fionread.c #include <sys/ioctl.h> main() { printf("%#08x\n", FIONREAD); } ^D % cc -o fionread fionread % ./fionread 0x4004667f
And then hard-code it, leaving porting as an exercise to your successor.
$FIONREAD = 0x4004667f; # XXX: opsys dependent
$size = pack("L", 0); ioctl(FH, $FIONREAD, $size) or die "Couldn't call ioctl: $!\n"; $size = unpack("L", $size);
FIONREAD requires a filehandle connected to a stream, meaning sockets, pipes, and tty devices work, but not files.