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File::Data - interface to file data


Wraps all the accessing of a file into a convenient set of calls for reading and writing data, including a simple regex interface.

Note that the file needs to exist prior to using this module!

See new()


        use strict;
        use File::Data;
        my $o_dat = File::Data->new('./t/example');
        $o_dat->write("complete file contents\n");
        $o_dat->prepend("first line\n"); # line 0
        $o_dat->append("original second (last) line\n");
        $o_dat->insert(2, "new second line\n"); # inc. zero!
        $o_dat->replace('line', 'LINE');
        print $o_dat->READ;

    Or, perhaps more seriously :-}

        my $o_sgm = File::Data->new('./sgmlfile');
        print "new SGML data: ".$o_sgm->REPLACE(
        ) if $o_sgm;



lowercase method calls return the object itself, so you can chain calls.

    my $o_obj = $o_dat->read; # ! <= object !

UPPERCASE method calls return the data relevant to the operation.

    my @data  = $o_dat->READ; # ! <= data   !

While this may occasionally be frustrating, using the principle of least surprise, it is at least consistent.

See do


    The idea is to standardise accessing of files for repetitive and straight forward tasks, and remove the repeated and therefore error prone file access I have seen in many sites, where varying, (with equivalently varying success), methods are used to achieve essentially the same result - a simple search and replace and/or a regex match.

    Approaches to opening and working with files vary so much, where one person may wish to know if a file exists, another wishes to know whether the target is a file, or if it is readable, or writable and so on. Sometimes, in production code even (horror), file's are opened without any checks of whether the open was successful. Then there's a loop through each line to find the first or many patterns to read and/or replace. With a failure, normally the only message is 'permission denied', is that read or write access, does the file even exist? etc.

    This module attempts to provide a plain/generic interface to accessing a file's data. This will not suit every situation, but I have included some examples which will hopefully demonstrate that it may be used in situations where people would normally go through varying and inconsistent, (and therefore error-prone), procedures - to get at the same data.

    Theoretically you can mix and match your read and writes so long as you don't open read-only.

        my $o_dat  = File::Data->new($file);
        my $i_snrd = $o_dat->append($append)->REPLACE($search, $replace);
        print $o_dat->READ;

    If you want to apply the same regex, or insert/prepend/replacement/whatever mechanism, to many different files, then the neatest solution may be to do something like the following:

        foreach my $file ( @list_of_file_names ) {
            my $o_dat  = File::Data->new($file);
            my $i_snrd = $o_dat->append($append)->REPLACE($search, $replace);
            print $o_dat->READ;

    One last thing - I'm sure this could be made more efficient, and I'd be receptive to any suggestions to that effect. Note though that the intention has been to create a simple and consistent interface, rather than a complicated one.



Create a new File::Data object (default read-write).

    my $o_rw = File::Data->new($filename); # read-write

    my $o_ro = File::Data->new($filename, 'ro'); # read-only

Each file should have it's own discrete object.

Note that if you open a file read-only and then attempt to write to it, that will be regarded as an error, even if you change the permissions in the meantime.

Further: The file must exist before successful use of this method is possible. This is not a replacement for modules which create and delete files, this is purely designed as an interface to the data of existing files. A create function is a future possibility.

Look in EXAMPLES for a more complete explanation of possible arguments to the new() method


Read all data from file

    $o_dat = $o_dat->read; # !

    my @data = $o_dat->READ;


    does this...

Write data to file

    my $o_dat = $o_dat->WRITE; # !

    my @written = $o_dat->write;

Prepend to file

    my $o_dat = $o_dat->prepen(\@lines); # !

    my @prepended = $o_dat->prepend(\@lines);

Insert data at line number, starting from '0'

    my $o_dat = $o_dat->insert($i_lineno, \@lines); # !

    my @inserted = $o_dat->INSERT($i_lineno, \@lines);

Append to file

    my $o_dat = $o_dat->append(\@lines); # !

    my @appended = $o_dat->APPEND(\@lines);

Retrieve data out of a file, simple list of all matches found are returned.

Note - you must use capturing parentheses for this to work!

    my $o_dat = $o_dat->search('^(.*\@.*)$'); # !

    my @addrs = $o_dat->SEARCH('^(.*\@.*)$');

    my @names = $o_dat->SEARCH('^(?:[^:]:){4}([^:]+):');

Replace data in a 'search and replace' manner, returns the final data.

    my $o_dat = $o_dat->replace($search, $replace); # !

    my @data = $o_dat->REPLACE($search, $replace);

    my @data = $o_dat->REPLACE(
        q|\<a href=(['"])([^$1]+)?$1| => q|''|,

This is simple, in that you can do almost anything in the search side, but the replace side is a bit more restricted, as we can't effect the replacement modifiers on the fly.

If you really need this, perhaps (?{}) can help?


Returns the product of the given (or last) do(), undef on failure.

    my $o_dat = $o_dat->prepend($A)->append($b)->return('prepend'); # !

    my @prepended = $o_dat->prepend($A)->append($b)->RETURN('prepend');

    my @appended  = $o_dat->prepend($A)->append($b)->RETURN; # like read()

placeholder - unsupported


placeholder - unsupported


Close the file

    my $i_closed = $o_dat->close; # 1|0

placeholder - unsupported


Various variables may be set affecting the behaviour of the module.


Set to 0 (default) or 1 for debugging information to be printed on STDOUT.

    $File::Data::DEBUG = 1;

Alternatively set to a regex of any of the prime methods to debug them individually.

    $File::Data::DEBUG = '(ap|pre)pend';

Will die if there is any failure in accessing the file, or reading the data.

Default = 0 (don't die - just warn);

    $File::Data::FATAL = 1;    # die

Will return a reference, not a list, useful with large files.

Default is 0, ie; methods normally returns a list. There may be an argument to make returns work with references by default, feedback will decide.

    $File::Data::REFERENCE = 1;

    my $a_ref = $o_dat->search('.*');

    print "The log: \n".@{ $a_ref };

Set to something other than zero if you don't want error messages ?-\

    $File::Data::SILENT = 0; # per line

Where regex's are used, default behaviour is to treate the entire file as a single scalar string, so that, for example, (?ms:...) matches are effective.

Unset if you don't want this behaviour.

    $File::Data::STRING = 0; # per line

File will be opened read-write (insert() compatible) unless this variable is set explicitly or given via new(). In either case, unless it is one of our valid permission keys declared below, it will be passed on to FileHandle and otherwise not modified. We don't support fancy permission sets, just read or write.

Read-only permissions may be explicitly set using one of these keys:

    $File::Data::PERMISSIONS = 'ro'; # or readonly or <

Or, equivalently, for read-write (default):

    $File::Data::PERMISSIONS = 'rw'; # or readwrite or +<

Note that it makes no sense to have an 'append only' command (>>), we'd have to disable all of write, search and replace, and insert, etc. in that case - just use the append() method only.

This is a KISS-compatible module remember?

# ================================================================




Any unrecognised function will be passed to the FileHandle object for final consideration, behaviour is then effectively 'o_dat ISA FileHandle'.



Typical construction examples:

    my $o_rw = File::Data->new($filename, 'rw');

    my $o_ro = File::Data->new($filename, 'ro');
    my $o_dat = File::Data->new('./jabber');

    $o_dat->write("  Bewxre the Jabberwock my son,\n");

    $o_dat->prepend("The Jxbberwock by Lewis Cxrroll:\n");

    $o_dat->append("  the claws thxt snxtch,\n  ...\n");

    $o_dat->insert(2, "  the jaws which bite.\n");

    $o_dat->replace('x', 'a');

    print $o_dat->SEARCH('The.+\n')->REPLACE("The.+\n", '')->return('search');

    print $o_dat->READ;

Failure is indicated by an error routine being called, this will print out any error to STDERR, unless warnings are declared fatal, in which case we croak. You can register your own error handlers for any method mentioned in the METHOD section of this document, in addition is a special init call for initial file opening and general setting up.

Create a read-write object with a callback for all errors:

    my $o_rw = File::Data->new($filename, 'ro', {
        'error'        => \&myerror,

Create a read-only object with a separate object handler for each error type:

    my $o_rw = File::Data->new($filename, 'rw', {
        'error'        => $o_generic->error_handler,
        'insert'    => $o_handler->insert_error,
        'open'        => $o_open_handler,
        'read'        => \&carp,
        'write'        => \&write_error,

From the command line:

    C<perl -MFile::Data -e "File::Data->new('./test.txt')->write('some stuff')">

And (very non-obfuscated)

  perl -MFile::Data -e "@x=sort qw(perl another hacker just);
    print map {split(\"\n\", ucfirst(\$_).\" \")}\
      write(shift(@x).\"\n\")->    \
      append(shift(@x).\"\n\")->   \
      prepend(shift(@x).\"\n\")->  \
      insert(2, shift(@x).\"\n\")->\

If you still have problems, mail me the output of

    make test TEST_VERBOSE=1

Simple wrapper for method calls, returning the content.

    my @inserted = $o_dat->do('insert', @this);

    my @appended = $o_dat->do('append', @this);

An addendum to this method, and to make life generally easier, is that you can also call any of the above methods in uppercase, to call via do() eg;

    my @data = $o_dat->WRITE($this)->APPEND->($that)->read;

First argument is the method to call, followed by the arguments that method expects.

    perl -MFile::Data -e "print File::Data->new($file)->INSERT(3,
    \"third line\n\")->READ";

If you want to get at the output of a particular called method see return()


Richard Foley <>


Copyright (C) 2016 by Richard Foley

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.