File::GlobMapper
File::GlobMapper(3) User Contributed Perl Documentation File::GlobMapper(3)
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 opera-
tions 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 cur-
rent 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;
}
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 parameter operates just like the replace-
ment part of a substitute command. The difference is that the "#1"
syntax is used to reference sub-patterns matched in the input file-
glob, rather than the $1 syntax that is used with perl regular expres-
sions. 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 struc-
ture 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
~
~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 com-
plete 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 file-
name.
#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>’
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.
perl v5.8.8 2009-02-04 File::GlobMapper(3)
