=encoding utf8
=head1 NAME
POSIX::1003::Fcntl - POSIX function fcntl
=head1 SYNOPSIS
use POSIX::1003::Fcntl;
=head1 DESCRIPTION
One function, which hides many tricks with file-descriptors. This module
tries to provide functions which separates the various uses.
=head1 FUNCTIONS
=head2 Standard POSIX
=over 4
=item B<fcntl>($fd, $function, SCALAR)
See C<perlfunc fcntl>. This raw call to C<fcntl()> is only in some
cases simple, but often isn't.
=item B<flockfd>($fd, $flags)
Not standard POSIX, but available on many POSIX platforms. Often
implemented as L<fcntl()|POSIX::1003::Fcntl/"Standard POSIX">, which is more complex to use. On other
platforms implemented as separate OS feature.
Perl core provides a C<flock> which may hide plaform differences.
This C<flockfd> is the pure version. Try to use L<setfd_lock()|POSIX::1003::Fcntl/"Additional">, which
is more portable and flexible.
example:
use POSIX::1003::Fcntl ':flock';
if(flockfd $fd, LOCK_EX|LOCK_NB) ...
flockfd $fd, LOCK_UN;
=item B<lockf>($fd, $flag, $length)
Not standard POSIX, but available on many POSIX platforms. Often
implemented via L<fcntl()|POSIX::1003::Fcntl/"Standard POSIX">, which is more complex to use.
example:
use POSIX::1003::Fcntl ':lockfd';
if(lockf $fd, F_LOCK) ...
lockf $fd, F_ULOCK;
=back
=head2 Additional
=over 4
=item B<fcntl_dup>($fd|$fh, %options)
Commands F_DUPFD and F_DUPFD_CLOEXEC: dupplicate a file-descriptor
to the lowest free fd number.
-Option --Default
close_on_exec <false>
=over 2
=item close_on_exec => BOOLEAN
=back
example:
my $dup_fd = fcntl_dup \*STDOUT;
my $dup_fd = fcntl_dup 2, close_on_exec => 1;
=item B<getfd_control>($fd|$fh)
Control the file descriptor flags, command F_GETFD.
=item B<getfd_flags>($fd|$fh)
Get the file status flags and access modes, command F_GETFL.
example:
my $flags = getfd_flags(fd);
if ((flags & O_ACCMODE) == O_RDWR)
=item B<getfd_islocked>($fd|$fh, %options)
Command F_GETLCK. Returns the first lock which would prevent getting
the lock. The %options are the same as for L<setfd_lock()|POSIX::1003::Fcntl/"Additional">.
example:
if(my $lock = getfd_islocked \*IN) ...
=item B<getfd_lease>($fd|$fh)
Command F_GETLEASE.
example:
my $lease = getfd_lease(\*STDIN) or die $!;
if($lease != F_RDLCK) ...
=item B<getfd_owner>($fd|$fh, %options)
Commands F_GETOWN and F_GETOWN_EX.
example:
my ($type, $pid) = getfd_owner($fd);
defined $type or die $!;
if($type==F_OWNER_PGRP) ...
my $pid = getfd_owner($fd) or die $!;
=item B<getfd_pipe_size>($fd|$fh)
Command F_GETPIPE_SZ.
example:
my $size = getfd_pipe_size($pipe) or die $!;
=item B<getfd_signal>($fd|$fh)
Command F_GETSIG.
example:
my $signal = getfd_signal(\*STDOUT) or die $!;
=item B<setfd_control>($fd|$fh, $flags)
Change the file descriptor flags, command F_SETFD.
=item B<setfd_flags>($fd|$fh, $flags)
Change the file status flags and access modes, command F_SETFL.
=item B<setfd_lease>($fd|$fh, $flags)
Command F_SETLEASE.
example:
setfd_lease(\*STDOUT, F_WRLCK) or die $!;
=item B<setfd_lock>($fd|$fh, %options)
Commands F_SETLKP and F_SETLKWP.
Request a lock for (a section of) a file.
-Option --Default
len <until end of file>
private <false>
start 0
type F_RDLCK
wait <false>
whence SEEK_SET
=over 2
=item len => BLOCK_LENGTH
=item private => BOOLEAN
Linux kernel >= 3.15 provides "open file description locks", also known
as "file-private POSIX locks". Use them when available.
=item start => FILEPOS
=item type => F_RDLCK|F_WRLCK|F_UNLCK
=item wait => BOOLEAN
=item whence => SEEK_SET|SEEK_CUR|SEEK_END
=back
example:
setfd_lock \*IN, type => F_WRLCK, wait => 1
or die "cannot lock IN: $!\n";
=item B<setfd_notify>($fd|$fh, $flags)
Command F_NOTIFY.
example:
my $d = openfd('/etc', O_RDONLY|O_DIRECTORY) or die $!;
setfd_notify($d, DN_ACCESS|DN_CREATE|DN_MULTISHOT) or die $!;
=item B<setfd_owner>($fd|$fh, $pid, %options)
Commands F_GETOWN and F_GETOWN_EX. The _EX version is attempted
if provided.
-Option--Default
type <looks at sign>
=over 2
=item type => F_OWNER_TID|F_OWNER_PID|F_OWNER_PGRP
=back
example:
setfd_owner($fh, $pid) or die $!;
setfd_owner($fh, $pid, type => F_OWNER_TID) or die $!;
setfd_owner($fh, -9); # $pid=9, type=F_OWNER_PGRP
=item B<setfd_pipe_size>($fd|$fh, $size)
Command F_SETPIPE_SZ.
example:
setfd_pipe_size($pipe, 16384) or die $!;
=item B<setfd_signal>($fd|$fh, $signal)
Command F_SETSIG.
example:
setfd_signal(\*STDOUT, SIGINT) or die $!;
=back
=head1 CONSTANTS
The following constants are exported, shown here with the values
discovered during installation of this module.
=for comment
#TABLE_FCNTL_START
The constant names for this fcntl module are inserted here during
installation.
=for comment
#TABLE_FCNTL_END
=head1 SEE ALSO
This module is part of POSIX-1003 distribution version 1.02,
built on November 10, 2020. Website: F<http://perl.overmeer.net/CPAN>. The code is based on L<POSIX>, which
is released with Perl itself. See also L<POSIX::Util> for
additional functionality.
=head1 COPYRIGHTS
Copyrights 2011-2020 on the perl code and the related documentation
by [Mark Overmeer]. For other contributors see ChangeLog.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://dev.perl.org/licenses/>