=encoding utf8

=head1 NAME

POSIX::1003 - POSIX 1003.1-2008 provisioning

=head1 SYNOPSIS

  use POSIX::1003           qw(:termios :pc PATH_MAX);
  # is short for all of these:
  use POSIX::1003::Termios  qw(:all);
  use POSIX::1003::Pathconf qw(:all);
  use POSIX::1003::FS       qw(PATH_MAX);

  # full modules, subsets, constants, functions
  use POSIX::1003           qw(:pathconf :stat R_OK, cos);

  # overview about all exported symbols (by a module)
  show_posix_names 'POSIX::1003::Pathconf';
  show_posix_names ':pc';
  perl -MPOSIX::1003 'show_posix_names'

=head1 DESCRIPTION

The L<POSIX::1003|POSIX::1003> suite provides access to b<many> POSIX functions. The
POSIX module in I<core> (distributed with Perl itself) is ancient, the
documentation is usually wrong, and it has too much unusable code in it.
C<POSIX::1003> tries to provide cleaner access to the operating system.
More about the choices made can be found in section L</Rationale>.

=head2 POSIX

The official POSIX standard is large, with over 1200 functions;
L<POSIX::Overview|POSIX::Overview> does list them all. This collection of C<POSIX::1003>
extension provides access to quite a number of those functions, when they
are not provided by "core". They also define as many system constants
as possible. More functions may get added in the future.

B<Start looking> in L<POSIX::Overview|POSIX::Overview>, to discover which module
provides certain functionality. You may also guess the location from
the module names listed in L</DETAILS>, below.

=head2 Bulk loading

It can be quite some work to work-out which modules define what symbols
and then write down all the explicit C<require> lines. Using bulk loading
via this C<POSIX::1003> will be slower during the import (because it needs
to load the location of each of the hundreds of symbols into memory),
but provides convenience: it loads the right modules automagically.

=head3 Exporter

This module uses nasty export tricks, so is not based in Exporter.
Some modules have more than one tag related to them, and one tag may
load multiple modules. When you do not specify symbol or tag, then B<all>
are loaded into your namespace(!), the same behavior as POSIX has.

If your import list starts with C<+1>, the symbols will not get into
your own namespace, but that of your caller. Just like
C<$Exporter::ExportLevel> (but a simpler syntax).

  use POSIX::1003 ':pathconf';
  use POSIX::1003 ':pc';       # same, abbreviated name
  use POSIX::1003 ':stat';     # subset from :filesystem

  use POSIX::1003 qw(PATH_MAX :math sin);

  sub MyModule::import(@)      # your own tricky exporter
  {   POSIX::1003->import('+1', @_);
  }

=head3 EXPORT_TAGS including whole modules

  (export tag)          (module)
  :all                  <all symbols, default>
  :cs      :confstr     POSIX::1003::Confstr
  :errno   :errors      POSIX::1003::Errno
  :ev      :events      POSIX::1003::Events
           :fcntl       POSIX::1003::Fcntl
  :fd      :fdio        POSIX::1003::FdIO
  :fs      :filesystem  POSIX::1003::FS
  :limit   :limits      POSIX::1003::Limit
  :locale               POSIX::1003::Locale
  :math                 POSIX::1003::Math
  :none                 (nothing)
  :os      :opsys       POSIX::1003::OS
  :pc      :pathconf    POSIX::1003::Pathconf
  :proc    :processes   POSIX::1003::Proc
  :props   :properties  POSIX::1003::Properties
  :posix   :property    POSIX::1003::Properties
  :sc      :sysconf     POSIX::1003::Sysconf
  :signals              POSIX::1003::Signals
  :signals :sigaction   POSIX::SigAction
  :signals :sigset      POSIX::SigSet
  :socket               POSIX::1003::Socket
  :termio  :termios     POSIX::1003::Termios
  :time                 POSIX::1003::Time
  :user                 POSIX::1003::User

=head3 EXPORT_TAGS including subsets

[0.96] Besides loading all the symbols of a module, you can also
include a subset for some of the modules

   (module)       (export tags for subsets)
   :fcntl         :flock   :lockf
   :fdio          :mode    :seek
   :filesystem    :access  :stat    :glob
   :limits        :rlimit  :ulimit
   :signals       :status  :signals
   :termios       :flush   :flags   :speed
   :socket        :sock    :sol     :so     :af    :pf

=head1 FUNCTIONS

=over 4

=item B<posix_1003_modules>()

Returns the names of all modules in the current release of POSIX::1003.

=item B<posix_1003_names>( [$modules|$tags] )

Returns  all the names, when in LIST content.  In SCALAR context,
it returns (a reference to) an HASH which contains exported names
to modules mappings.  If no explicit $modules are specified, then all
available modules are taken.

=item B<show_posix_names>( [$modules|$tags] )

Print all names defined by the POSIX::1003 suite in alphabetical
(case-insensitive) order. If no explicit $modules are specified, then all
available modules are taken.

=back

=head1 DETAILS

=head2 Modules in this distribution

=over 4

=item L<POSIX::1003::Confstr|POSIX::1003::Confstr>

Provide access to the C<_CS_*> constants.

=item L<POSIX::1003::Errno|POSIX::1003::Errno>

Provide access to the C<E*> constants, for error numbers, and strerror().

=item L<POSIX::1003::FdIO|POSIX::1003::FdIO>

Provides unbuffered IO handling; based on file-descriptors.

=item L<POSIX::1003::FS|POSIX::1003::FS>

Some generic file-system information. See also L<POSIX::1003::Pathconf|POSIX::1003::Pathconf>
for more precise info.

=item L<POSIX::1003::Locale|POSIX::1003::Locale>

Locales, see also L<perllocale>.

=item L<POSIX::1003::Math|POSIX::1003::Math>

Standard math functions of unknown precission.

=item L<POSIX::1003::OS|POSIX::1003::OS>

A few ways to get Operating system information.
See also L<POSIX::1003::Sysconf|POSIX::1003::Sysconf>, L<POSIX::1003::Confstr|POSIX::1003::Confstr>, and
L<POSIX::1003::Properties|POSIX::1003::Properties>,

=item L<POSIX::1003::Pathconf|POSIX::1003::Pathconf>

Provide access to the C<pathconf()> and its trillion C<_PC_*> constants.

=item L<POSIX::1003::Properties|POSIX::1003::Properties>

Provide access to the C<_POSIX_*> constants.

=item L<POSIX::1003::Signals|POSIX::1003::Signals>

With helper modules L<POSIX::SigSet|POSIX::SigSet> and L<POSIX::SigAction|POSIX::SigAction>.

=item L<POSIX::1003::Socket|POSIX::1003::Socket>

Provide access to many socket related constants.

=item L<POSIX::1003::Sysconf|POSIX::1003::Sysconf>

Provide access to the C<sysconf> and its zillion C<_SC_*> constants.

=item L<POSIX::1003::Termios|POSIX::1003::Termios>

Terminal IO

=item L<POSIX::1003::Time|POSIX::1003::Time>

Time-stamp processing

=item L<POSIX::1003::User|POSIX::1003::User>

Change active user and group.

=item L<POSIX::1003::Limit|POSIX::1003::Limit>

For getting and setting resource limits.

=back

=head2 Other modules

=over 4

=item User::pwent

Provides an OO interface around C<getpw*()>

=item User::grent

Provides an OO interface around C<getgr*()>

=back

=head2 Rationale

The POSIX module as distributed with Perl itself is ancient (it dates
before Perl5)  Although it proclaims that it provides access to all
POSIX functions, it only lists about 200 out of 1200. From that subset,
half of the functions will croak when you use them, complaining that
they cannot get implemented in Perl for some reason.

Many other functions provided by POSIX-in-Core simply forward the caller
to a function with the same name which is in basic perl (see perldoc).
With a few serious complications: the functions in POSIX do not use
prototypes, sometimes expect different arguments and sometimes return
different values.

Back to the basics: the L<POSIX::1003|POSIX::1003> provides access to the POSIX
libraries where they can be made compatible with Perl's way of doing
things. For instance, C<setuid> of POSIX is implemented with C<$)>,
whose exact behavior depends on compile-flags and OS: it's not the pure
C<setuid()> of the standard hence left-out. There is no C<isalpha()>
either: not compatible with Perl strings and implemented very different
interface from POSIX. And there is also no own C<exit()>, because we have
a C<CORE::exit()> with the same functionality.

=head2 POSIX::1003 compared to POSIX.pm

This distribution uses POSIX.xs (which is always available and ported to
all platforms) where it can, but adds much, much more.

When you are used to POSIX.pm but want to move to L<POSIX::1003|POSIX::1003>,
you must be aware about the following differences:

=over 4

=item *

the constants and functions are spread over many separate modules,
based on their purpose, where POSIX uses a header filename as
tag to group provided functionality.

=item *

functions provided by CORE are usually not exported again by POSIX::1003
(unless to avoid confusion, for instance: is C<atan2()> in core or
::Math?)  Importing those is therefore a silent no-op.

=item *

constants which are already provided via Fcntl or Errno are
not provided by this module as well. This should reduce the chance
for confusion.

=item *

functions which are also in CORE can be imported, but will silently
be ignored. In C<POSIX>, functions with the same name get exported
without prototype, which does have consequences for interpretation of
your program.  This module uses prototypes on all exported functions,
like CORE does.

=item *

hundreds of C<E*>, C<_SC_*>, C<_CS_*>, C<_PC_*>, C<_POSIX_*>, C<UL_*>,
and C<RLIMIT_*> constants were collected from various sources, not just
a minimal subset. You get access to all defined on your system.

=item *

when an user program addresses a constant which is not defined by the
system, POSIX will croak. Modules in POSIX::1003 on the other hand,
will return C<undef>.

This simplifies code like this:

  use POSIX::1003::FS         'PATH_MAX';
  use POSIX::1003::PathConfig '_PC_PATH_MAX';
  my $max_fn = _PC_PATH_MAX($fn) // PATH_MAX // 1024;

With the tranditional POSIX, you have to C<eval()> each use
of a constant.

=back

=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/>

