[perl5.git] / ext / NDBM_File / NDBM_File.pm

package NDBM_File;

use strict;
use warnings;

require Tie::Hash;
require XSLoader;

our @ISA = qw(Tie::Hash);
our $VERSION = "1.13";

XSLoader::load();

1;

__END__

=head1 NAME

NDBM_File - Tied access to ndbm files

=head1 SYNOPSIS

  use Fcntl;   # For O_RDWR, O_CREAT, etc.
  use NDBM_File;

  tie(%h, 'NDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
    or die "Couldn't tie NDBM file 'filename': $!; aborting";

  # Now read and change the hash
  $h{newkey} = newvalue;
  print $h{oldkey};
  ...

  untie %h;

=head1 DESCRIPTION

C<NDBM_File> establishes a connection between a Perl hash variable and
a file in NDBM_File format;.  You can manipulate the data in the file
just as if it were in a Perl hash, but when your program exits, the
data will remain in the file, to be used the next time your program
runs.

Use C<NDBM_File> with the Perl built-in C<tie> function to establish
the connection between the variable and the file.  The arguments to
C<tie> should be:

=over 4

=item 1.

The hash variable you want to tie.

=item 2.

The string C<"NDBM_File">.  (Ths tells Perl to use the C<NDBM_File>
package to perform the functions of the hash.)

=item 3.

The name of the file you want to tie to the hash.

=item 4.

Flags.  Use one of:

=over 2

=item C<O_RDONLY>

Read-only access to the data in the file.

=item C<O_WRONLY>

Write-only access to the data in the file.

=item C<O_RDWR>

Both read and write access.

=back

If you want to create the file if it does not exist, add C<O_CREAT> to
any of these, as in the example.  If you omit C<O_CREAT> and the file
does not already exist, the C<tie> call will fail.

=item 5.

The default permissions to use if a new file is created.  The actual
permissions will be modified by the user's umask, so you should
probably use 0666 here. (See L<perlfunc/umask>.)

=back

=head1 DIAGNOSTICS

On failure, the C<tie> call returns an undefined value and probably
sets C<$!> to contain the reason the file could not be tied.

=head2 C<ndbm store returned -1, errno 22, key "..." at ...>

This warning is emitted when you try to store a key or a value that
is too long.  It means that the change was not recorded in the
database.  See BUGS AND WARNINGS below.

=head1 BUGS AND WARNINGS

There are a number of limits on the size of the data that you can
store in the NDBM file.  The most important is that the length of a
key, plus the length of its associated value, may not exceed 1008
bytes.

See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl>

=cut
Commit	Line	Data
a0d0e21e LW	1	package NDBM_File;
a0d0e21e LW	2
698828ad JH	3	use strict;
698828ad JH	4	use warnings;
96318ac8 PM	5
96318ac8 PM	6	require Tie::Hash;
da4061d3	7	require XSLoader;
a0d0e21e	8
17f410f9	9	our @ISA = qw(Tie::Hash);
c4f76144	10	our $VERSION = "1.13";
c07a80fd	11
da4061d3	12	XSLoader::load();
a0d0e21e LW	13
	14	1;
	15
	16	__END__
a5f75d66 AD	17
	18	=head1 NAME
	19
	20	NDBM_File - Tied access to ndbm files
	21
	22	=head1 SYNOPSIS
	23
0fbd2a46 JH	24	use Fcntl; # For O_RDWR, O_CREAT, etc.
0fbd2a46 JH	25	use NDBM_File;
a5f75d66	26
d554b888 MS	27	tie(%h, 'NDBM_File', 'filename', O_RDWR\|O_CREAT, 0666)
	28	or die "Couldn't tie NDBM file 'filename': $!; aborting";
	29
0fbd2a46 JH	30	# Now read and change the hash
0fbd2a46 JH	31	$h{newkey} = newvalue;
d554b888	32	print $h{oldkey};
0fbd2a46	33	...
bbc7dcd2	34
0fbd2a46	35	untie %h;
bbc7dcd2	36
0fbd2a46	37	=head1 DESCRIPTION
bbc7dcd2	38
0fbd2a46 JH	39	C<NDBM_File> establishes a connection between a Perl hash variable and
	40	a file in NDBM_File format;. You can manipulate the data in the file
	41	just as if it were in a Perl hash, but when your program exits, the
	42	data will remain in the file, to be used the next time your program
	43	runs.
a5f75d66	44
0fbd2a46 JH	45	Use C<NDBM_File> with the Perl built-in C<tie> function to establish
	46	the connection between the variable and the file. The arguments to
	47	C<tie> should be:
a5f75d66	48
0fbd2a46 JH	49	=over 4
	50
	51	=item 1.
	52
	53	The hash variable you want to tie.
	54
d554b888	55	=item 2.
0fbd2a46 JH	56
	57	The string C<"NDBM_File">. (Ths tells Perl to use the C<NDBM_File>
	58	package to perform the functions of the hash.)
	59
d554b888	60	=item 3.
0fbd2a46	61
d554b888	62	The name of the file you want to tie to the hash.
0fbd2a46 JH	63
	64	=item 4.
	65
	66	Flags. Use one of:
	67
	68	=over 2
	69
	70	=item C<O_RDONLY>
	71
	72	Read-only access to the data in the file.
	73
	74	=item C<O_WRONLY>
	75
	76	Write-only access to the data in the file.
	77
	78	=item C<O_RDWR>
	79
	80	Both read and write access.
	81
	82	=back
	83
	84	If you want to create the file if it does not exist, add C<O_CREAT> to
	85	any of these, as in the example. If you omit C<O_CREAT> and the file
	86	does not already exist, the C<tie> call will fail.
	87
	88	=item 5.
	89
	90	The default permissions to use if a new file is created. The actual
	91	permissions will be modified by the user's umask, so you should
	92	probably use 0666 here. (See L<perlfunc/umask>.)
	93
	94	=back
	95
	96	=head1 DIAGNOSTICS
	97
	98	On failure, the C<tie> call returns an undefined value and probably
	99	sets C<$!> to contain the reason the file could not be tied.
	100
	101	=head2 C<ndbm store returned -1, errno 22, key "..." at ...>
	102
3c4b39be	103	This warning is emitted when you try to store a key or a value that
0fbd2a46 JH	104	is too long. It means that the change was not recorded in the
	105	database. See BUGS AND WARNINGS below.
	106
	107	=head1 BUGS AND WARNINGS
	108
	109	There are a number of limits on the size of the data that you can
	110	store in the NDBM file. The most important is that the length of a
	111	key, plus the length of its associated value, may not exceed 1008
	112	bytes.
a5f75d66	113
0fbd2a46	114	See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl>
a5f75d66 AD	115
a5f75d66 AD	116	=cut