Provided by: libapp-info-perl_0.57-1_all 
NAME
App::Info::Util - Utility class for App::Info subclasses
SYNOPSIS
use App::Info::Util;
my $util = App::Info::Util->new;
# Subclasses File::Spec.
my @paths = $util->paths;
# First directory that exists in a list.
my $dir = $util->first_dir(@paths);
# First directory that exists in a path.
$dir = $util->first_path($ENV{PATH});
# First file that exists in a list.
my $file = $util->first_file('this.txt', '/that.txt', 'C:\\foo.txt');
# First file found among file base names and directories.
my $files = ['this.txt', 'that.txt'];
$file = $util->first_cat_file($files, @paths);
DESCRIPTION
This class subclasses File::Spec and adds its own methods in order to offer utility
methods to App::Info classes. Although intended to be used by App::Info subclasses, in
truth App::Info::Util's utility may be considered more general, so feel free to use it
elsewhere.
The methods added in addition to the usual File::Spec suspects are designed to facilitate
locating files and directories on the file system, as well as searching those files. The
assumption is that, in order to provide useful meta data about a given software package,
an App::Info subclass must find relevant files and directories and parse them with regular
expressions. This class offers methods that simplify those tasks.
CONSTRUCTOR
new
my $util = App::Info::Util->new;
This is a very simple constructor that merely returns an App::Info::Util object. Since,
like its File::Spec super class, App::Info::Util manages no internal data itself, all
methods may be used as class methods, if one prefers to. The constructor here is provided
merely as a convenience.
OBJECT METHODS
In addition to all of the methods offered by its super class, File::Spec, App::Info::Util
offers the following methods.
first_dir
my @paths = $util->paths;
my $dir = $util->first_dir(@dirs);
Returns the first file system directory in @paths that exists on the local file system.
Only the first item in @paths that exists as a directory will be returned; any other paths
leading to non-directories will be ignored.
first_path
my $path = $ENV{PATH};
$dir = $util->first_path($path);
Takes the $path string and splits it into a list of directory paths, based on the path
delimiter on the local file system. Then calls "first_dir()" to return the first directory
in the path list that exists on the local file system. The path delimiter is specified for
the following file systems:
• MacOS: ","
• MSWin32: ";"
• os2: ";"
• VMS: undef
This method always returns undef on VMS. Patches welcome.
• epoc: undef
This method always returns undef on epoch. Patches welcome.
• Unix: ":"
All other operating systems are assumed to be Unix-based.
first_file
my $file = $util->first_file(@filelist);
Examines each of the files in @filelist and returns the first one that exists on the file
system. The file must be a regular file -- directories will be ignored.
first_exe
my $exe = $util->first_exe(@exelist);
Examines each of the files in @exelist and returns the first one that exists on the file
system as an executable file. Directories will be ignored.
first_cat_path
my $file = $util->first_cat_path('ick.txt', @paths);
$file = $util->first_cat_path(['this.txt', 'that.txt'], @paths);
The first argument to this method may be either a file or directory base name (that is, a
file or directory name without a full path specification), or a reference to an array of
file or directory base names. The remaining arguments constitute a list of directory
paths. "first_cat_path()" processes each of these directory paths, concatenates (by the
method native to the local operating system) each of the file or directory base names, and
returns the first one that exists on the file system.
For example, let us say that we were looking for a file called either httpd or apache, and
it could be in any of the following paths: /usr/local/bin, /usr/bin/, /bin. The method
call looks like this:
my $httpd = $util->first_cat_path(['httpd', 'apache'], '/usr/local/bin',
'/usr/bin/', '/bin');
If the OS is a Unix variant, "first_cat_path()" will then look for the first file that
exists in this order:
/usr/local/bin/httpd
/usr/local/bin/apache
/usr/bin/httpd
/usr/bin/apache
/bin/httpd
/bin/apache
The first of these complete paths to be found will be returned. If none are found, then
undef will be returned.
first_cat_dir
my $dir = $util->first_cat_dir('ick.txt', @paths);
$dir = $util->first_cat_dir(['this.txt', 'that.txt'], @paths);
Functionally identical to "first_cat_path()", except that it returns the directory path in
which the first file was found, rather than the full concatenated path. Thus, in the above
example, if the file found was /usr/bin/httpd, while "first_cat_path()" would return that
value, "first_cat_dir()" would return /usr/bin instead.
first_cat_exe
my $exe = $util->first_cat_exe('ick.exe', @paths);
$exe = $util->first_cat_exe(['this.exe', 'that.exe'], @paths);
Functionally identical to "first_cat_path()", except that it returns the full path to the
first executable file found, rather than simply the first file found.
search_file
my $file = 'foo.txt';
my $regex = qr/(text\s+to\s+find)/;
my $value = $util->search_file($file, $regex);
Opens $file and executes the $regex regular expression against each line in the file. Once
the line matches and one or more values is returned by the match, the file is closed and
the value or values returned.
For example, say foo.txt contains the line "Version 6.5, patch level 8", and you need to
grab each of the three version parts. All three parts can be grabbed like this:
my $regex = qr/Version\s+(\d+)\.(\d+),[^\d]*(\d+)/;
my @nums = $util->search_file($file, $regex);
Now @nums will contain the values "(6, 5, 8)". Note that in a scalar context, the above
search would yield an array reference:
my $regex = qr/Version\s+(\d+)\.(\d+),[^\d]*(\d+)/;
my $nums = $util->search_file($file, $regex);
So now $nums contains "[6, 5, 8]". The same does not hold true if the match returns only
one value, however. Say foo.txt contains the line "king of the who?", and you wish to know
who the king is king of. Either of the following two calls would get you the data you
need:
my $minions = $util->search_file($file, qr/King\s+of\s+(.*)/);
my @minions = $util->search_file($file, qr/King\s+of\s+(.*)/);
In the first case, because the regular expression contains only one set of parentheses,
"search_file()" will simply return that value: $minions contains the string "the who?". In
the latter case, @minions of course contains a single element: "("the who?")".
Note that a regular expression without parentheses -- that is, one that doesn't grab
values and put them into $1, $2, etc., will never successfully match a line in this
method. You must include something to parenthetically match. If you just want to know the
value of what was matched, parenthesize the whole thing and if the value returns, you have
a match. Also, if you need to match patterns across lines, try using multiple regular
expressions with "multi_search_file()", instead.
files_in_dir
my @files = $util->files_in_dir($dir);
@files = $util->files_in_dir($dir, $filter);
my $files = $util->files_in_dir($dir);
$files = $util->files_in_dir($dir, $filter);
Returns an list or array reference of all of the files and directories in the file system
directory $dir. An optional second argument is a code reference that filters the files.
The code reference should examine the $_ for a file name and return true if it's a file
that you're interested and false if it's not.
multi_search_file
my @regexen = (qr/(one)/, qr/(two)\s+(three)/);
my @matches = $util->multi_search_file($file, @regexen);
Like "search_file()", this method opens $file and parses it for regular expression
matches. This method, however, can take a list of regular expressions to look for, and
will return the values found for all of them. Regular expressions that match and return
multiple values will be returned as array references, while those that match and return a
single value will return just that single value.
For example, say you are parsing a file with lines like the following:
#define XML_MAJOR_VERSION 1
#define XML_MINOR_VERSION 95
#define XML_MICRO_VERSION 2
You need to get each of these numbers, but calling "search_file()" for each of them would
be wasteful, as each call to "search_file()" opens the file and parses it. With
"multi_search_file()", on the other hand, the file will be opened only once, and, once all
of the regular expressions have returned matches, the file will be closed and the matches
returned.
Thus the above values can be collected like this:
my @regexen = ( qr/XML_MAJOR_VERSION\s+(\d+)$/,
qr/XML_MINOR_VERSION\s+(\d+)$/,
qr/XML_MICRO_VERSION\s+(\d+)$/ );
my @nums = $file->multi_search_file($file, @regexen);
The result will be that @nums contains "(1, 95, 2)". Note that "multi_file_search()" tries
to do the right thing by only parsing the file until all of the regular expressions have
been matched. Thus, a large file with the values you need near the top can be parsed very
quickly.
As with "search_file()", "multi_search_file()" can take regular expressions that match
multiple values. These will be returned as array references. For example, say the file
you're parsing has files like this:
FooApp Version 4
Subversion 2, Microversion 6
To get all of the version numbers, you can either use three regular expressions, as in the
previous example:
my @regexen = ( qr/FooApp\s+Version\s+(\d+)$/,
qr/Subversion\s+(\d+),/,
qr/Microversion\s+(\d$)$/ );
my @nums = $file->multi_search_file($file, @regexen);
In which case @nums will contain "(4, 2, 6)". Or, you can use just two regular
expressions:
my @regexen = ( qr/FooApp\s+Version\s+(\d+)$/,
qr/Subversion\s+(\d+),\s+Microversion\s+(\d$)$/ );
my @nums = $file->multi_search_file($file, @regexen);
In which case @nums will contain "(4, [2, 6])". Note that the two parentheses that return
values in the second regular expression cause the matches to be returned as an array
reference.
lib_dirs
my @dirs = $util->lib_dirs;
Returns a list of possible library directories to be searched. These are gathered from the
"libsdirs" and "loclibpth" Config settings. These are useful for passing to
"first_cat_dir()" to search typical directories for library files.
SUPPORT
This module is stored in an open GitHub repository <http://github.com/theory/app-info/>.
Feel free to fork and contribute!
Please file bug reports via GitHub Issues <http://github.com/theory/app-info/issues/> or
by sending mail to bug-App-Info@rt.cpan.org <mailto:bug-App-Info@rt.cpan.org>.
AUTHOR
David E. Wheeler <david@justatheory.com>
SEE ALSO
App::Info, File::Spec, App::Info::HTTPD::Apache App::Info::RDBMS::PostgreSQL
COPYRIGHT AND LICENSE
Copyright (c) 2002-2011, David E. Wheeler. Some Rights Reserved.
This module is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.