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Man Pages


Manual Reference Pages  -  TIE::FILE::ASHASH (3)

.ds Aq ’

NAME

Tie::File::AsHash - Like Tie::File but access lines using a hash instead of an array

CONTENTS

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 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 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 isnt 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>

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. 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(1)
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perl v5.20.3 TIE::FILE::ASHASH (3) 2006-04-07

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