NAME
POSIX::1003::Fcntl - POSIX function fcntl
SYNOPSIS
use POSIX::1003::Fcntl;DESCRIPTION
One function, which hides many tricks with file-descriptors. This module tries to provide functions which separates the various uses.
FUNCTIONS
Standard POSIX
- fcntl($fd, $function, SCALAR)
-
See
perlfunc fcntl. This raw call tofcntl()is only in some cases simple, but often isn't. - flockfd($fd, $flags)
-
Not standard POSIX, but available on many POSIX platforms. Often implemented as fcntl(), which is more complex to use. On other platforms implemented as separate OS feature.
Perl core provides a
flockwhich may hide plaform differences. Thisflockfdis the pure version. Try to use setfd_lock(), which is more portable and flexible.example:
use POSIX::1003::Fcntl ':flock'; if(flockfd $fd, LOCK_EX|LOCK_NB) ... flockfd $fd, LOCK_UN; - lockf($fd, $flag, $length)
-
Not standard POSIX, but available on many POSIX platforms. Often implemented via fcntl(), which is more complex to use.
example:
use POSIX::1003::Fcntl ':lockfd'; if(lockf $fd, $fcntl->{F_LOCK}) ... lockf $fd, $fcntl->{F_ULOCK};
Additional
- fcntl_dup($fd|$fh, %options)
-
Functions $fcntl->{F_DUPFD} and $fcntl->{F_DUPFD_CLOEXEC}: dupplicate a file-descriptor to the lowest free fd number.
-Option --Default close_on_exec <false>example:
my $dup_fd = fcntl_dup \*STDOUT; my $dup_fd = fcntl_dup 2, close_on_exec => 1; - getfd_control($fd|$fh)
-
Control the file descriptor flags, function $fcntl->{F_GETFD}.
- getfd_flags($fd|$fh)
-
Get the file status flags and access modes, function $fcntl->{F_GETFL}.
example:
my $flags = getfd_flags(fd); if ((flags & O_ACCMODE) == O_RDWR) - getfd_islocked($fd|$fh, %options)
-
Function $fcntl->{F_GETLCK}. Returns the first lock which would prevent getting the lock. The %options are the same as for setfd_lock().
example:
if(my $lock = getfd_islocked \*IN) ... - getfd_lease($fd|$fh)
-
Function $fcntl->{F_GETLEASE}.
example:
my $lease = getfd_lease(\*STDIN) or die $!; if($lease != $fcntl->{F_RDLCK}) ... - getfd_owner($fd|$fh, %options)
-
Function $fcntl->{F_GETOWN} or $fcntl->{F_GETOWN_EX}.
example:
my ($type, $pid) = getfd_owner($fd); defined $type or die $!; if($type==$fcntl->{F_OWNER_PGRP}) ... my $pid = getfd_owner($fd) or die $!; - getfd_pipe_size($fd|$fh)
-
Function $fcntl->{F_GETPIPE_SZ}.
example:
my $size = getfd_pipe_size($pipe) or die $!; - getfd_signal($fd|$fh)
-
Function $fcntl->{F_GETSIG}.
example:
my $signal = getfd_signal(\*STDOUT) or die $!; - setfd_control($fd|$fh, $flags)
-
Change the file descriptor flags, function $fcntl->{F_SETFD}.
- setfd_flags($fd|$fh, $flags)
-
Change the file status flags and access modes, function $fcntl->{F_SETFL}.
- setfd_lease($fd|$fh, $flags)
-
Function $fcntl->{F_SETLEASE}.
example:
setfd_lease(\*STDOUT, $fcntl->{F_WRLCK}) or die $!; - setfd_lock($fd|$fh, %options)
-
Functions $fcntl->{F_SETLK} and $fcntl->{F_SETLKW}: request a lock for (a section of) a file.
-Option --Default len <until end of file> private <false> start 0 type $fcntl->{F_RDLCK} wait <false> whence SEEK_SET- len => BLOCK_LENGTH
- private => BOOLEAN
-
Linux kernel >= 3.15 provides "open file description locks", also known as "file-private POSIX locks". Use them when available.
- start => FILEPOS
- type => $fcntl->{F_RDLCK}|$fcntl->{F_WRLCK}|$fcntl->{F_UNLCK}
- wait => BOOLEAN
- whence => SEEK_SET|SEEK_CUR|SEEK_END
example:
setfd_lock \*IN, type => $fcntl->{F_WRLCK}, wait => 1 or die "cannot lock IN: $!\n"; - setfd_notify($fd|$fh, $flags)
-
Function $fcntl->{F_NOTIFY}.
example:
my $d = openfd('/etc', O_RDONLY|O_DIRECTORY) or die $!; setfd_notify($d, DN_ACCESS|DN_CREATE|DN_MULTISHOT) or die $!; - setfd_owner($fd|$fh, $pid, %options)
-
Function $fcntl->{F_GETOWN} or $fcntl->{F_GETOWN_EX}. The _EX version is attempted if provided.
-Option--Default type <looks at sign>example:
setfd_owner($fh, $pid) or die $!; setfd_owner($fh, $pid, type => $fcntl->{F_OWNER_TID}) or die $!; setfd_owner($fh, -9); # $pid=9, type=$fcntl->{F_OWNER_PGRP} - setfd_pipe_size($fd|$fh, $size)
-
Function $fcntl->{F_SETPIPE_SZ}.
example:
setfd_pipe_size($pipe, 16384) or die $!; - setfd_signal($fd|$fh, $signal)
-
Function $fcntl->{F_SETSIG}.
example:
setfd_signal(\*STDOUT, SIGINT) or die $!;
CONSTANTS
The following constants are exported, shown here with the values discovered during installation of this module.
DN_ACCESS 1 F_SETFL 4
DN_ATTRIB 32 F_SETLEASE 1024
DN_CREATE 4 F_SETLKW 7
DN_DELETE 8 F_SETOWN 8
DN_MODIFY 2 F_SETOWN_EX 15
DN_MULTISHOT 2147483648 F_SETPIPE_SZ 1031
DN_RENAME 16 F_SETSIG 10
F_DUPFD 0 F_TEST 3
F_DUPFD_CLOEXEC 1030 F_TLOCK 2
F_GETFD 1 F_ULOCK 0
F_GETFL 3 F_UNLCK 2
F_GETLEASE 1025 F_WRLCK 1
F_GETLK 5 FAPPEND 1024
F_GETOWN 9 FASYNC 8192
F_GETOWN_EX 16 FD_CLOEXEC 1
F_GETPIPE_SZ 1032 FNDELAY 2048
F_GETSIG 11 FNONBLOCK 2048
F_LOCK 1 LOCK_EX 2
F_NOTIFY 1026 LOCK_NB 4
F_RDLCK 0 LOCK_SH 1
F_SETFD 2 LOCK_UN 8SEE ALSO
This module is part of POSIX-1003 distribution version 0.99_01, built on January 31, 2015. Website: http://perl.overmeer.net. The code is based on POSIX, which is released with Perl itself. See also POSIX::Util for additional functionality.
COPYRIGHTS
Copyrights 2011-2015 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 http://www.perl.com/perl/misc/Artistic.html