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man : File::GlobMapper
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
WARNING Alpha Release Alert!
o This code is a work in progress.
o There are known bugs.
o The interface defined here is tentative.
o There are portability issues.
o Do not use in production code.
o Consider yourself warned!
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
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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;
}
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
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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
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.
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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
~
~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
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*.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;
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>'
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To uncompress
'</my/home/*.[ch].gz>' '</my/home/#1.#2>'
SEE ALSO
File::Glob
AUTHOR
The File::GlobMapper module was written by Paul Marquess,
pmqsATcpan.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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