


File::GlobMapper(Perl Programmers Reference GFile::GlobMapper(3p)


NAME
       File::GlobMapper - Extend File Glob to Allow Input and
       Output Files

SYNOPSIS
           use File::GlobMapper qw( globmap );

           my $aref = globmap $input => $output
               or die $File::GlobMapper::Error ;

           my $gm = new File::GlobMapper $input => $output
               or die $File::GlobMapper::Error ;

DESCRIPTION
       This module needs Perl5.005 or better.

       This module takes the existing "File::Glob" module as a
       starting point and extends it to allow new filenames to be
       derived from the files matched by "File::Glob".

       This can be useful when carrying out batch operations on
       multiple files that have both an input filename and output
       filename and the output file can be derived from the input
       filename. Examples of operations where this can be useful
       include, file renaming, file copying and file compression.

   Behind The Scenes
       To help explain what "File::GlobMapper" does, consider
       what code you would write if you wanted to rename all
       files in the current directory that ended in ".tar.gz" to
       ".tgz". So say these files are in the current directory

           alpha.tar.gz
           beta.tar.gz
           gamma.tar.gz

       and they need renamed to this

           alpha.tgz
           beta.tgz
           gamma.tgz

       Below is a possible implementation of a script to carry
       out the rename (error cases have been omitted)

           foreach my $old ( glob "*.tar.gz" )
           {
               my $new = $old;
               $new =~ s#(.*)\.tar\.gz$#$1.tgz# ;

               rename $old => $new
                   or die "Cannot rename '$old' to '$new': $!\n;
           }




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       Notice that a file glob pattern "*.tar.gz" was used to
       match the ".tar.gz" files, then a fairly similar regular
       expression was used in the substitute to allow the new
       filename to be created.

       Given that the file glob is just a cut-down regular
       expression and that it has already done a lot of the hard
       work in pattern matching the filenames, wouldn't it be
       handy to be able to use the patterns in the fileglob to
       drive the new filename?

       Well, that's exactly what "File::GlobMapper" does.

       Here is same snippet of code rewritten using "globmap"

           for my $pair (globmap '<*.tar.gz>' => '<#1.tgz>' )
           {
               my ($from, $to) = @$pair;
               rename $from => $to
                   or die "Cannot rename '$old' to '$new': $!\n;
           }

       So how does it work?

       Behind the scenes the "globmap" function does a
       combination of a file glob to match existing filenames
       followed by a substitute to create the new filenames.

       Notice how both parameters to "globmap" are strings that
       are delimited by <>.  This is done to make them look more
       like file globs - it is just syntactic sugar, but it can
       be handy when you want the strings to be visually
       distinctive. The enclosing <> are optional, so you don't
       have to use them - in fact the first thing globmap will do
       is remove these delimiters if they are present.

       The first parameter to "globmap", "*.tar.gz", is an Input
       File Glob.  Once the enclosing "< ... >" is removed, this
       is passed (more or less) unchanged to "File::Glob" to
       carry out a file match.

       Next the fileglob "*.tar.gz" is transformed behind the
       scenes into a full Perl regular expression, with the
       additional step of wrapping each transformed wildcard
       metacharacter sequence in parenthesis.

       In this case the input fileglob "*.tar.gz" will be
       transformed into this Perl regular expression

           ([^/]*)\.tar\.gz

       Wrapping with parenthesis allows the wildcard parts of the
       Input File Glob to be referenced by the second parameter
       to "globmap", "#1.tgz", the Output File Glob. This



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File::GlobMapper(Perl Programmers Reference GFile::GlobMapper(3p)


       parameter operates just like the replacement part of a
       substitute command. The difference is that the "#1" syntax
       is used to reference sub-patterns matched in the input
       fileglob, rather than the $1 syntax that is used with perl
       regular expressions. In this case "#1" is used to refer to
       the text matched by the "*" in the Input File Glob. This
       makes it easier to use this module where the parameters to
       "globmap" are typed at the command line.

       The final step involves passing each filename matched by
       the "*.tar.gz" file glob through the derived Perl regular
       expression in turn and expanding the output fileglob using
       it.

       The end result of all this is a list of pairs of
       filenames. By default that is what is returned by
       "globmap". In this example the data structure returned
       will look like this

            ( ['alpha.tar.gz' => 'alpha.tgz'],
              ['beta.tar.gz'  => 'beta.tgz' ],
              ['gamma.tar.gz' => 'gamma.tgz']
            )

       Each pair is an array reference with two elements - namely
       the from filename, that "File::Glob" has matched, and a to
       filename that is derived from the from filename.

   Limitations
       "File::GlobMapper" has been kept simple deliberately, so
       it isn't intended to solve all filename mapping
       operations. Under the hood "File::Glob" (or for older
       versions of Perl, "File::BSDGlob") is used to match the
       files, so you will never have the flexibility of full Perl
       regular expression.

   Input File Glob
       The syntax for an Input FileGlob is identical to
       "File::Glob", except for the following

       1.   No nested {}

       2.   Whitespace does not delimit fileglobs.

       3.   The use of parenthesis can be used to capture parts
            of the input filename.

       4.   If an Input glob matches the same file more than
            once, only the first will be used.

       The syntax

       ~




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File::GlobMapper(Perl Programmers Reference GFile::GlobMapper(3p)


       ~user
       .    Matches a literal '.'.  Equivalent to the Perl
            regular expression

                \.

       *    Matches zero or more characters, except '/'.
            Equivalent to the Perl regular expression

                [^/]*

       ?    Matches zero or one character, except '/'. Equivalent
            to the Perl regular expression

                [^/]?

       \    Backslash is used, as usual, to escape the next
            character.

       []   Character class.

       {,}  Alternation

       ()   Capturing parenthesis that work just like perl

       Any other character it taken literally.

   Output File Glob
       The Output File Glob is a normal string, with 2 glob-like
       features.

       The first is the '*' metacharacter. This will be replaced
       by the complete filename matched by the input file glob.
       So

           *.c *.Z

       The second is

       Output FileGlobs take the

       "*"  The "*" character will be replaced with the complete
            input filename.

       #1   Patterns of the form /#\d/ will be replaced with the

   Returned Data
EXAMPLES
   A Rename script
       Below is a simple "rename" script that uses "globmap" to
       determine the source and destination filenames.

           use File::GlobMapper qw(globmap) ;
           use File::Copy;



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           die "rename: Usage rename 'from' 'to'\n"
               unless @ARGV == 2 ;

           my $fromGlob = shift @ARGV;
           my $toGlob   = shift @ARGV;

           my $pairs = globmap($fromGlob, $toGlob)
               or die $File::GlobMapper::Error;

           for my $pair (@$pairs)
           {
               my ($from, $to) = @$pair;
               move $from => $to ;
           }

       Here is an example that renames all c files to cpp.

           $ rename '*.c' '#1.cpp'

   A few example globmaps
       Below are a few examples of globmaps

       To copy all your .c file to a backup directory

           '</my/home/*.c>'    '</my/backup/#1.c>'

       If you want to compress all

           '</my/home/*.[ch]>'    '<*.gz>'

       To uncompress

           '</my/home/*.[ch].gz>'    '</my/home/#1.#2>'

SEE ALSO
       File::Glob

AUTHOR
       The File::GlobMapper module was written by Paul Marquess,
       pmqs@cpan.org.

COPYRIGHT AND LICENSE
       Copyright (c) 2005 Paul Marquess. All rights reserved.
       This program is free software; you can redistribute it
       and/or modify it under the same terms as Perl itself.











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