Implements the fcntl(2) function. You'll probably have to say
use Fcntl;
first to get the correct constant definitions. Argument processing and value returned work just like ioctl
below. For example:
use Fcntl;
my $flags = fcntl($filehandle, F_GETFL, 0)
or die "Can't fcntl F_GETFL: $!";
You don't have to check for defined
on the return from fcntl
. Like 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 Argument "..." isn't numeric
warnings on improper numeric conversions.
Note that fcntl
raises an exception 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);
my $flags = fcntl($REMOTE, F_GETFL, 0)
or die "Can't get flags for the socket: $!\n";
fcntl($REMOTE, F_SETFL, $flags | O_NONBLOCK)
or die "Can't set flags for the socket: $!\n";
Portability issues: "fcntl" in perlport.