1File::GlobMapper(3pm)  Perl Programmers Reference Guide  File::GlobMapper(3pm)
2
3
4

NAME

6       File::GlobMapper - Extend File Glob to Allow Input and Output Files
7

SYNOPSIS

9           use File::GlobMapper qw( globmap );
10
11           my $aref = globmap $input => $output
12               or die $File::GlobMapper::Error ;
13
14           my $gm = new File::GlobMapper $input => $output
15               or die $File::GlobMapper::Error ;
16

DESCRIPTION

18       This module needs Perl5.005 or better.
19
20       This module takes the existing "File::Glob" module as a starting point
21       and extends it to allow new filenames to be derived from the files
22       matched by "File::Glob".
23
24       This can be useful when carrying out batch operations on multiple files
25       that have both an input filename and output filename and the output
26       file can be derived from the input filename. Examples of operations
27       where this can be useful include, file renaming, file copying and file
28       compression.
29
30   Behind The Scenes
31       To help explain what "File::GlobMapper" does, consider what code you
32       would write if you wanted to rename all files in the current directory
33       that ended in ".tar.gz" to ".tgz". So say these files are in the
34       current directory
35
36           alpha.tar.gz
37           beta.tar.gz
38           gamma.tar.gz
39
40       and they need renamed to this
41
42           alpha.tgz
43           beta.tgz
44           gamma.tgz
45
46       Below is a possible implementation of a script to carry out the rename
47       (error cases have been omitted)
48
49           foreach my $old ( glob "*.tar.gz" )
50           {
51               my $new = $old;
52               $new =~ s#(.*)\.tar\.gz$#$1.tgz# ;
53
54               rename $old => $new
55                   or die "Cannot rename '$old' to '$new': $!\n;
56           }
57
58       Notice that a file glob pattern "*.tar.gz" was used to match the
59       ".tar.gz" files, then a fairly similar regular expression was used in
60       the substitute to allow the new filename to be created.
61
62       Given that the file glob is just a cut-down regular expression and that
63       it has already done a lot of the hard work in pattern matching the
64       filenames, wouldn't it be handy to be able to use the patterns in the
65       fileglob to drive the new filename?
66
67       Well, that's exactly what "File::GlobMapper" does.
68
69       Here is same snippet of code rewritten using "globmap"
70
71           for my $pair (globmap '<*.tar.gz>' => '<#1.tgz>' )
72           {
73               my ($from, $to) = @$pair;
74               rename $from => $to
75                   or die "Cannot rename '$old' to '$new': $!\n;
76           }
77
78       So how does it work?
79
80       Behind the scenes the "globmap" function does a combination of a file
81       glob to match existing filenames followed by a substitute to create the
82       new filenames.
83
84       Notice how both parameters to "globmap" are strings that are delimited
85       by <>.  This is done to make them look more like file globs - it is
86       just syntactic sugar, but it can be handy when you want the strings to
87       be visually distinctive. The enclosing <> are optional, so you don't
88       have to use them - in fact the first thing globmap will do is remove
89       these delimiters if they are present.
90
91       The first parameter to "globmap", "*.tar.gz", is an Input File Glob.
92       Once the enclosing "< ... >" is removed, this is passed (more or less)
93       unchanged to "File::Glob" to carry out a file match.
94
95       Next the fileglob "*.tar.gz" is transformed behind the scenes into a
96       full Perl regular expression, with the additional step of wrapping each
97       transformed wildcard metacharacter sequence in parenthesis.
98
99       In this case the input fileglob "*.tar.gz" will be transformed into
100       this Perl regular expression
101
102           ([^/]*)\.tar\.gz
103
104       Wrapping with parenthesis allows the wildcard parts of the Input File
105       Glob to be referenced by the second parameter to "globmap", "#1.tgz",
106       the Output File Glob. This parameter operates just like the replacement
107       part of a substitute command. The difference is that the "#1" syntax is
108       used to reference sub-patterns matched in the input fileglob, rather
109       than the $1 syntax that is used with perl regular expressions. In this
110       case "#1" is used to refer to the text matched by the "*" in the Input
111       File Glob. This makes it easier to use this module where the parameters
112       to "globmap" are typed at the command line.
113
114       The final step involves passing each filename matched by the "*.tar.gz"
115       file glob through the derived Perl regular expression in turn and
116       expanding the output fileglob using it.
117
118       The end result of all this is a list of pairs of filenames. By default
119       that is what is returned by "globmap". In this example the data
120       structure returned will look like this
121
122            ( ['alpha.tar.gz' => 'alpha.tgz'],
123              ['beta.tar.gz'  => 'beta.tgz' ],
124              ['gamma.tar.gz' => 'gamma.tgz']
125            )
126
127       Each pair is an array reference with two elements - namely the from
128       filename, that "File::Glob" has matched, and a to filename that is
129       derived from the from filename.
130
131   Limitations
132       "File::GlobMapper" has been kept simple deliberately, so it isn't
133       intended to solve all filename mapping operations. Under the hood
134       "File::Glob" (or for older versions of Perl, "File::BSDGlob") is used
135       to match the files, so you will never have the flexibility of full Perl
136       regular expression.
137
138   Input File Glob
139       The syntax for an Input FileGlob is identical to "File::Glob", except
140       for the following
141
142       1.   No nested {}
143
144       2.   Whitespace does not delimit fileglobs.
145
146       3.   The use of parenthesis can be used to capture parts of the input
147            filename.
148
149       4.   If an Input glob matches the same file more than once, only the
150            first will be used.
151
152       The syntax
153
154       ~
155       ~user
156       .    Matches a literal '.'.  Equivalent to the Perl regular expression
157
158                \.
159
160       *    Matches zero or more characters, except '/'. Equivalent to the
161            Perl regular expression
162
163                [^/]*
164
165       ?    Matches zero or one character, except '/'. Equivalent to the Perl
166            regular expression
167
168                [^/]?
169
170       \    Backslash is used, as usual, to escape the next character.
171
172       []   Character class.
173
174       {,}  Alternation
175
176       ()   Capturing parenthesis that work just like perl
177
178       Any other character it taken literally.
179
180   Output File Glob
181       The Output File Glob is a normal string, with 2 glob-like features.
182
183       The first is the '*' metacharacter. This will be replaced by the
184       complete filename matched by the input file glob. So
185
186           *.c *.Z
187
188       The second is
189
190       Output FileGlobs take the
191
192       "*"  The "*" character will be replaced with the complete input
193            filename.
194
195       #1   Patterns of the form /#\d/ will be replaced with the
196
197   Returned Data

EXAMPLES

199   A Rename script
200       Below is a simple "rename" script that uses "globmap" to determine the
201       source and destination filenames.
202
203           use File::GlobMapper qw(globmap) ;
204           use File::Copy;
205
206           die "rename: Usage rename 'from' 'to'\n"
207               unless @ARGV == 2 ;
208
209           my $fromGlob = shift @ARGV;
210           my $toGlob   = shift @ARGV;
211
212           my $pairs = globmap($fromGlob, $toGlob)
213               or die $File::GlobMapper::Error;
214
215           for my $pair (@$pairs)
216           {
217               my ($from, $to) = @$pair;
218               move $from => $to ;
219           }
220
221       Here is an example that renames all c files to cpp.
222
223           $ rename '*.c' '#1.cpp'
224
225   A few example globmaps
226       Below are a few examples of globmaps
227
228       To copy all your .c file to a backup directory
229
230           '</my/home/*.c>'    '</my/backup/#1.c>'
231
232       If you want to compress all
233
234           '</my/home/*.[ch]>'    '<*.gz>'
235
236       To uncompress
237
238           '</my/home/*.[ch].gz>'    '</my/home/#1.#2>'
239

SEE ALSO

241       File::Glob
242

AUTHOR

244       The File::GlobMapper module was written by Paul Marquess,
245       pmqs@cpan.org.
246
248       Copyright (c) 2005 Paul Marquess. All rights reserved.  This program is
249       free software; you can redistribute it and/or modify it under the same
250       terms as Perl itself.
251
252
253
254perl v5.12.4                      2011-06-07             File::GlobMapper(3pm)
Impressum