Implements the fcntl(2) function. You'll probably have to say
first to get the correct constant definitions. Argument processing and value return works just like
ioctl below. For example:
use Fcntl; fcntl($filehandle, F_GETFL, $packed_return_buffer) or die "can't fcntl F_GETFL: $!";
You don't have to check for
defined on the return from
ioctl, it maps a
0 return from the system call into
"0 but true" in Perl. This string is true in boolean context and
0 in numeric context. It is also exempt from the normal -w warnings on improper numeric conversions.
fcntl will produce a fatal error if used on a machine that doesn't implement fcntl(2). See the Fcntl module or your fcntl(2) manpage to learn what functions are available on your system.
Here's an example of setting a filehandle named
REMOTE to be non-blocking at the system level. You'll have to negotiate
$| on your own, though.
use Fcntl qw(F_GETFL F_SETFL O_NONBLOCK); $flags = fcntl(REMOTE, F_GETFL, 0) or die "Can't get flags for the socket: $!\n"; $flags = fcntl(REMOTE, F_SETFL, $flags | O_NONBLOCK) or die "Can't set flags for the socket: $!\n";