File::GlobMapper(3p) Perl Programmers Reference Guide File::GlobMapper(3p) #
File::GlobMapper(3p) Perl Programmers Reference Guide File::GlobMapper(3p)
NNAAMMEE #
File::GlobMapper - Extend File Glob to Allow Input and Output Files
SSYYNNOOPPSSIISS #
use File::GlobMapper qw( globmap );
my $aref = globmap $input => $output
or die $File::GlobMapper::Error ;
my $gm = File::GlobMapper->new( $input => $output )
or die $File::GlobMapper::Error ;
DDEESSCCRRIIPPTTIIOONN #
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.
BBeehhiinndd TThhee SScceenneess 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;
}
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 _e_x_a_c_t_l_y 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 _I_n_p_u_t _F_i_l_e _G_l_o_b.
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
_O_u_t_p_u_t _F_i_l_e _G_l_o_b. 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 _f_r_o_m
filename, that "File::Glob" has matched, and a _t_o filename that is
derived from the _f_r_o_m filename.
LLiimmiittaattiioonnss “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.
IInnppuutt FFiillee GGlloobb 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
~~
~~uusseerr
.. 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.
OOuuttppuutt FFiillee GGlloobb 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
RReettuurrnneedd DDaattaa
EEXXAAMMPPLLEESS #
AA RReennaammee ssccrriipptt 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'
AA ffeeww eexxaammppllee gglloobbmmaappss 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>'
SSEEEE AALLSSOO #
File::Glob
AAUUTTHHOORR #
The _F_i_l_e_:_:_G_l_o_b_M_a_p_p_e_r module was written by Paul Marquess, _p_m_q_s_@_c_p_a_n_._o_r_g.
CCOOPPYYRRIIGGHHTT AANNDD LLIICCEENNSSEE #
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 v5.36.3 2023-02-15 File::GlobMapper(3p)