Jens Rehsack > Tie-File-AsHash > Tie::File::AsHash

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Module Version: 0.200   Source  

NAME ^

Tie::File::AsHash - access lines of a file as a hash splitting at separator

SYNOPSIS ^

 use Tie::File::AsHash;

 tie my %hash, 'Tie::File::AsHash', 'filename', split => ':'
        or die "Problem tying %hash: $!";

 print $hash{foo};                  # access hash value via key name
 $hash{foo} = "bar";                # assign new value
 my @keys = keys %hash;             # get the keys
 my @values = values %hash;         # ... and values
 exists $hash{perl};                # check for existence
 delete $hash{baz};                 # delete line from file
 $hash{newkey} = "perl";            # entered at end of file
 while (($key,$val) = each %hash)   # iterate through hash
 %hash = ();                        # empty file

 untie %hash;                       # all done

Here is sample text that would work with the above code when contained in a file:

 foo:baz
 key:val
 baz:whatever

DESCRIPTION ^

Tie::File::AsHash uses Tie::File and perl code from Tie::Array::AsHash so files can be tied to hashes. Tie::File does all the hard work while Tie::File::AsHash works a little magic of its own.

The module was initially written by Chris Angell <chris@chrisangell.com> for managing htpasswd-format password files.

USAGE ^

 use Tie::File::AsHash;
 tie %hash, 'Tie::File::AsHash', 'filename', split => ':'
        or die "Problem tying %hash: $!";

 (use %hash like a regular ol' hash)

 untie %hash;  # changes saved to disk

Easy enough eh?

New key/value pairs are appended to the end of the file, delete removes lines from the file, keys and each work as expected, and so on.

Tie::File::AsHash will not die or exit if there is a problem tying a file, so make sure to check the return value and check $! as the examples do.

OPTIONS

The only argument Tie::File::AsHash requires is the "split" option, besides a filename. The split option's value is the delimiter that exists in the file between the key and value portions of the line. It may be a regular expression, and if so, the "join" option must be used to tell Tie::File::AsHash what to stick between the key and value when writing to the file. Otherwise, the module dies with an error message.

 tie %hash, 'Tie::File::AsHash', 'filename',  split => qr(\s+), join => " "
        or die "Problem tying %hash: $!";

Obviously no one wants lines like "key(?-xism:\s+)val" in their files.

All other options are passed directly to Tie::File, so read its documentation for more information.

CAVEATS ^

When keys, values, or each is used on the hash, the values are returned in the same order as the data exists in the file, from top to bottom, though this behavior should not be relied on and is subject to change at any time (but probably never will).

Tie::File::AsHash doesn't force keys to be unique. If there are multiple keys, the first key in the file, starting at the top, is used. However, when keys, values, or each is used on the hash, every key/value combination is returned, including duplicates, triplicates, etc.

Keys can't contain the split character. Look at the perl code that Tie::File::AsHash is comprised of to see why (look at the regexes). Using a regex for the split value may be one way around this issue.

Tie::File::AsHash hasn't been optimized much. Maybe it doesn't need to be. Optimization could add overhead. Maybe there can be options to turn on and off various types of optimization?

EXAMPLES ^

changepass.pl

changepass.pl changes password file entries when the lines are of "user:encryptedpass" format. It can also add users.

 #!/usr/bin/perl -w

 use strict;
 use Tie::File::AsHash;

 die "Usage: $0 user password" unless @ARGV == 2;
 my ($user, $newpass) = @ARGV;

 tie my %users, 'Tie::File::AsHash', '/pwdb/users.txt', split => ':'
     or die "Problem tying %hash: $!";

 # username isn't in the password file? see if the admin wants it added
 unless (exists $users{$user}) {

         print "User '$user' not found in db.  Add as a new user? (y/n)\n";
         chomp(my $y_or_n = <STDIN>);
         set_pw($user, $newpass) if $y_or_n =~ /^[yY]/;

 } else {

         set_pw($user, $newpass);
         print "Done.\n";

 }

 sub set_pw { $users{$_[0]} = crypt($_[1], "AA") }

Using the join option

Here's code that would allow the delimiter to be ':' or '#' but prefers '#':

 tie my %hash, 'Tie::File::AsHash', 'filename', split => qr/[:#]/, join => "#" or die $!;

Say you want to be sure no ':' delimiters exist in the file:

 while (my ($key, $val) = each %hash) {

        $hash{$key} = $val;

 }

AUTHOR ^

Chris Angell <chris@chrisangell.com>, Jens Rehsack <rehsack@web.de>

Feel free to email me with suggestions, fixes, etc.

Thanks to Mark Jason Dominus for authoring the superb Tie::File module.

COPYRIGHT ^

Copyright (C) 2004, Chris Angell, 2008-2013, Jens Rehsack. All Rights Reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, including any version of Perl 5.

SEE ALSO ^

perl(1), perltie(1), Tie::File(3pm), Tie::Array::AsHash(3pm)

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