Provided by: libpath-iterator-rule-perl_1.015-2_all 
NAME
Path::Iterator::Rule - Iterative, recursive file finder
VERSION
version 1.015
SYNOPSIS
use Path::Iterator::Rule;
my $rule = Path::Iterator::Rule->new; # match anything
$rule->file->size(">10k"); # add/chain rules
# iterator interface
my $next = $rule->iter( @dirs );
while ( defined( my $file = $next->() ) ) {
...
}
# list interface
for my $file ( $rule->all( @dirs ) ) {
...
}
DESCRIPTION
This module iterates over files and directories to identify ones matching a user-defined
set of rules. The API is based heavily on File::Find::Rule, but with more explicit
distinction between matching rules and options that influence how directories are
searched. A "Path::Iterator::Rule" object is a collection of rules (match criteria) with
methods to add additional criteria. Options that control directory traversal are given as
arguments to the method that generates an iterator.
Here is a summary of features for comparison to other file finding modules:
• provides many "helper" methods for specifying rules
• offers (lazy) iterator and flattened list interfaces
• custom rules implemented with callbacks
• breadth-first (default) or pre- or post-order depth-first searching
• follows symlinks (by default, but can be disabled)
• directories visited only once (no infinite loop; can be disabled)
• doesn't chdir during operation
• provides an API for extensions
As a convenience, the PIR module is an empty subclass of this one that is less arduous to
type for one-liners.
Note: paths are constructed with unix-style forward-slashes for efficiency rather than
using File::Spec. If proper path separators are needed, call canonpath on the search
results.
USAGE
Constructors
"new"
my $rule = Path::Iterator::Rule->new;
Creates a new rule object that matches any file or directory. It takes no arguments. For
convenience, it may also be called on an object, in which case it still returns a new
object that matches any file or directory.
"clone"
my $common = Path::Iterator::Rule->new->file->not_empty;
my $big_files = $common->clone->size(">1M");
my $small_files = $common->clone->size("<10K");
Creates a copy of a rule object. Useful for customizing different rule objects against a
common base.
Matching and iteration
"iter"
my $next = $rule->iter( @dirs, \%options);
while ( defined( my $file = $next->() ) ) {
...
}
Creates a subroutine reference iterator that returns a single result when dereferenced.
This iterator is "lazy" -- results are not pre-computed.
It takes as arguments a list of directories to search and an optional hash reference of
control options. If no search directories are provided, the current directory is used
("."). Valid options include:
• "depthfirst" -- Controls order of results. Valid values are "1" (post-order, depth-
first search), "0" (breadth-first search) or "-1" (pre-order, depth-first search).
Default is 0.
• "error_handler" -- Catches errors during execution of rule tests. Default handler dies
with the filename and error. If set to undef, error handling is disabled.
• "follow_symlinks" -- Follow directory symlinks when true. Default is 1.
• "report_symlinks" -- Includes symlinks in results when true. Default is equal to
"follow_symlinks".
• "loop_safe" -- Prevents visiting the same directory more than once when true. Default
is 1.
• "relative" -- Return matching items relative to the search directory. Default is 0.
• "sorted" -- Whether entries in a directory are sorted before processing. Default is 1.
• "visitor" -- An optional coderef that will be called on items matching all rules.
Filesystem loops might exist from either hard or soft links. The "loop_safe" option
prevents infinite loops, but adds some overhead by making "stat" calls. Because
directories are visited only once when "loop_safe" is true, matches could come from a
symlinked directory before the real directory depending on the search order.
To get only the real files, turn off "follow_symlinks". You can have symlinks included in
results, but not descend into symlink directories if you turn off "follow_symlinks", but
turn on "report_symlinks".
Turning "loop_safe" off and leaving "follow_symlinks" on avoids "stat" calls and will be
fastest, but with the risk of an infinite loop and repeated files. The default is slow,
but safe.
The "error_handler" parameter must be a subroutine reference. It will be called when a
rule test throws an exception. The first argument will be the file name being inspected
and the second argument will be the exception.
The optional "visitor" parameter must be a subroutine reference. If set, it will be
called for any result that matches. It is called the same way a custom rule would be (see
"EXTENDING") but its return value is ignored. It is called when an item is first
inspected -- "postorder" is not respected.
The paths inspected and returned will be relative to the search directories provided. If
these are absolute, then the paths returned will have absolute paths. If these are
relative, then the paths returned will have relative paths.
If the search directories are absolute and the "relative" option is true, files returned
will be relative to the search directory. Note that if the search directories are not
mutually exclusive (whether containing subdirectories like @INC or symbolic links), files
found could be returned relative to different initial search directories based on
"depthfirst", "follow_symlinks" or "loop_safe".
When the iterator is exhausted, it will return undef.
"iter_fast"
This works just like "iter", except that it optimizes for speed over safety. Don't do this
unless you're sure you need it and accept the consequences. See "PERFORMANCE" for
details.
"all"
my @matches = $rule->all( @dir, \%options );
Returns a list of paths that match the rule. It takes the same arguments and has the same
behaviors as the "iter" method. The "all" method uses "iter" internally to fetch all
results.
In scalar context, it will return the count of matched paths.
In void context, it is optimized to iterate over everything, but not store results. This
is most useful with the "visitor" option:
$rule->all( $path, { visitor => \&callback } );
"all_fast"
This works just like "all", except that it optimizes for speed over safety. Don't do this
unless you're sure you need it and accept the consequences. See "PERFORMANCE" for
details.
"test"
if ( $rule->test( $path, $basename, $stash ) ) { ... }
Test a file path against a rule. Used internally, but provided should someone want to
create their own, custom iteration algorithm.
Logic operations
"Path::Iterator::Rule" provides three logic operations for adding rules to the object.
Rules may be either a subroutine reference with specific semantics (described below in
"EXTENDING") or another "Path::Iterator::Rule" object.
"and"
$rule->and( sub { -r -w -x $_ } ); # stacked filetest example
$rule->and( @more_rules );
Adds one or more constraints to the current rule. E.g. "old rule AND new1 AND new2 AND
...". Returns the object to allow method chaining.
"or"
$rule->or(
$rule->new->name("foo*"),
$rule->new->name("bar*"),
sub { -r -w -x $_ },
);
Takes one or more alternatives and adds them as a constraint to the current rule. E.g.
"old rule AND ( new1 OR new2 OR ... )". Returns the object to allow method chaining.
"not"
$rule->not( sub { -r -w -x $_ } );
Takes one or more alternatives and adds them as a negative constraint to the current rule.
E.g. "old rule AND NOT ( new1 AND new2 AND ...)". Returns the object to allow method
chaining.
"skip"
$rule->skip(
$rule->new->dir->not_writeable,
$rule->new->dir->name("foo"),
);
Takes one or more alternatives and will prune a directory if any of the criteria match or
if any of the rules already indicate the directory should be pruned. Pruning means the
directory will not be returned by the iterator and will not be searched.
For files, it is equivalent to "$rule->not($rule->or(@rules))". Returns the object to
allow method chaining.
This method should be called as early as possible in the rule chain. See "skip_dirs"
below for further explanation and an example.
RULE METHODS
Rule methods are helpers that add constraints. Internally, they generate a closure to
accomplish the desired logic and add it to the rule object with the "and" method. Rule
methods return the object to allow for method chaining.
File name rules
"name"
$rule->name( "foo.txt" );
$rule->name( qr/foo/, "bar.*");
The "name" method takes one or more patterns and creates a rule that is true if any of the
patterns match the basename of the file or directory path. Patterns may be regular
expressions or glob expressions (or literal names).
"iname"
$rule->iname( "foo.txt" );
$rule->iname( qr/foo/, "bar.*");
The "iname" method is just like the "name" method, but matches case-insensitively.
"skip_dirs"
$rule->skip_dirs( @patterns );
The "skip_dirs" method skips directories that match one or more patterns. Patterns may be
regular expressions or globs (just like "name"). Directories that match will not be
returned from the iterator and will be excluded from further search. This includes the
starting directories. If that isn't what you want, see "skip_subdirs" instead.
Note: this rule should be specified early so that it has a chance to operate before a
logical shortcut. E.g.
$rule->skip_dirs(".git")->file; # OK
$rule->file->skip_dirs(".git"); # Won't work
In the latter case, when a ".git" directory is seen, the "file" rule shortcuts the rule
before the "skip_dirs" rule has a chance to act.
"skip_subdirs"
$rule->skip_subdirs( @patterns );
This works just like "skip_dirs", except that the starting directories (depth 0) are not
skipped and may be returned from the iterator unless excluded by other rules.
File test rules
Most of the "-X" style filetest are available as boolean rules. The table below maps the
filetest to its corresponding method name.
Test | Method Test | Method
------|------------- ------|----------------
-r | readable -R | r_readable
-w | writeable -W | r_writeable
-w | writable -W | r_writable
-x | executable -X | r_executable
-o | owned -O | r_owned
| |
-e | exists -f | file
-z | empty -d | directory, dir
-s | nonempty -l | symlink
| -p | fifo
-u | setuid -S | socket
-g | setgid -b | block
-k | sticky -c | character
| -t | tty
-T | ascii
-B | binary
For example:
$rule->file->nonempty; # -f -s $file
The -X operators for timestamps take a single argument in a form that Number::Compare can
interpret.
Test | Method
------|-------------
-A | accessed
-M | modified
-C | changed
For example:
$rule->modified(">1"); # -M $file > 1
Stat test rules
All of the "stat" elements have a method that takes a single argument in a form understood
by Number::Compare.
stat() | Method
--------------------
0 | dev
1 | ino
2 | mode
3 | nlink
4 | uid
5 | gid
6 | rdev
7 | size
8 | atime
9 | mtime
10 | ctime
11 | blksize
12 | blocks
For example:
$rule->size(">10K")
Depth rules
$rule->min_depth(3);
$rule->max_depth(5);
The "min_depth" and "max_depth" rule methods take a single argument and limit the paths
returned to a minimum or maximum depth (respectively) from the starting search directory.
A depth of 0 means the starting directory itself. A depth of 1 means its children. (This
is similar to the Unix "find" utility.)
Perl file rules
# All perl rules
$rule->perl_file;
# Individual perl file rules
$rule->perl_module; # .pm files
$rule->perl_pod; # .pod files
$rule->perl_test; # .t files
$rule->perl_installer; # Makefile.PL or Build.PL
$rule->perl_script; # .pl or 'perl' in the shebang
These rule methods match file names (or a shebang line) that are typical of Perl
distribution files.
Version control file rules
# Skip all known VCS files
$rule->skip_vcs;
# Skip individual VCS files
$rule->skip_cvs;
$rule->skip_rcs;
$rule->skip_svn;
$rule->skip_git;
$rule->skip_bzr;
$rule->skip_hg;
$rule->skip_darcs;
Skips files and/or prunes directories related to a version control system. Just like
"skip_dirs", these rules should be specified early to get the correct behavior.
File content rules
"contents_match"
$rule->contents_match(qr/BEGIN .* END/xs);
The "contents_match" rule takes a list of regular expressions and returns files that match
one of the expressions.
The expressions are applied to the file's contents as a single string. For large files,
this is likely to take significant time and memory.
Files are assumed to be encoded in UTF-8, but alternative Perl IO layers can be passed as
the first argument:
$rule->contents_match(":encoding(iso-8859-1)", qr/BEGIN .* END/xs);
See perlio for further details.
"line_match"
$rule->line_match(qr/^new/i, qr/^Addition/);
The "line_match" rule takes a list of regular expressions and returns files with at least
one line that matches one of the expressions.
Files are assumed to be encoded in UTF-8, but alternative Perl IO layers can be passed as
the first argument.
"shebang"
$rule->shebang(qr/#!.*\bperl\b/);
The "shebang" rule takes a list of regular expressions or glob patterns and checks them
against the first line of a file.
Other rules
"dangling"
$rule->symlink->dangling;
$rule->not_dangling;
The "dangling" rule method matches dangling symlinks. Use it or its inverse to control
how dangling symlinks should be treated.
Negated rules
Most rule methods have a negated form preceded by "not_".
$rule->not_name("foo.*")
Because this happens automatically, it includes somewhat silly ones like "not_nonempty"
(which is thus a less efficient way of saying "empty").
Rules that skip directories or version control files do not have a negated version.
EXTENDING
Custom rule subroutines
Rules are implemented as (usually anonymous) subroutine callbacks that return a value
indicating whether or not the rule matches. These callbacks are called with three
arguments. The first argument is a path, which is also locally aliased as the $_ global
variable for convenience in simple tests.
$rule->and( sub { -r -w -x $_ } ); # tests $_
The second argument is the basename of the path, which is useful for certain types of name
checks:
$rule->and( sub { $_[1] =~ /foo|bar/ } ); "foo" or "bar" in basename;
The third argument is a hash reference that can be used to maintain state. Keys beginning
with an underscore are reserved for "Path::Iterator::Rule" to provide additional data
about the search in progress. For example, the "_depth" key is used to support minimum
and maximum depth checks.
The custom rule subroutine must return one of four values:
• A true value -- indicates the constraint is satisfied
• A false value -- indicates the constraint is not satisfied
• "\1" -- indicate the constraint is satisfied, and prune if it's a directory
• "\0" -- indicate the constraint is not satisfied, and prune if it's a directory
A reference is a special flag that signals that a directory should not be searched
recursively, regardless of whether the directory should be returned by the iterator or
not.
The legacy "0 but true" value used previously for pruning is no longer valid and will
throw an exception if it is detected.
Here is an example. This is equivalent to the "max_depth" rule method with a depth of 3:
$rule->and(
sub {
my ($path, $basename, $stash) = @_;
return 1 if $stash->{_depth} < 3;
return \1 if $stash->{_depth} == 3;
return \0; # should never get here
}
);
Files and directories and directories up to depth 3 will be returned and directories will
be searched. Files of depth 3 will be returned. Directories of depth 3 will be returned,
but their contents will not be added to the search.
Returning a reference is "sticky" -- they will propagate through "and" and "or" logic.
0 && \0 = \0 \0 && 0 = \0 0 || \0 = \0 \0 || 0 = \0
0 && \1 = \0 \0 && 1 = \0 0 || \1 = \1 \0 || 1 = \1
1 && \0 = \0 \1 && 0 = \0 1 || \0 = \1 \1 || 0 = \1
1 && \1 = \1 \1 && 1 = \1 1 || \1 = \1 \1 || 1 = \1
Once a directory is flagged to be pruned, it will be pruned regardless of subsequent
rules.
$rule->max_depth(3)->name(qr/foo/);
This will return files or directories with "foo" in the name, but all directories at depth
3 will be pruned, regardless of whether they match the name rule.
Generally, if you want to do directory pruning, you are encouraged to use the "skip"
method instead of writing your own logic using "\0" and "\1".
Extension modules and custom rule methods
One of the strengths of File::Find::Rule is the many CPAN modules that extend it.
"Path::Iterator::Rule" provides the "add_helper" method to provide a similar mechanism for
extensions.
The "add_helper" class method takes three arguments, a "name" for the rule method, a
closure-generating callback, and a flag for not generating a negated form of the rule.
Unless the flag is true, an inverted "not_*" method is generated automatically. Extension
classes should call this as a class method to install new rule methods. For example, this
adds a "foo" method that checks if the filename is "foo":
package Path::Iterator::Rule::Foo;
use Path::Iterator::Rule;
Path::Iterator::Rule->add_helper(
foo => sub {
my @args = @_; # do this to customize closure with arguments
return sub {
my ($item, $basename) = @_;
return if -d "$item";
return $basename =~ /^foo$/;
}
}
);
1;
This allows the following rule methods:
$rule->foo;
$fule->not_foo;
The "add_helper" method will warn and ignore a helper with the same name as an existing
method.
Subclassing
Instead of processing and returning strings, this module may be subclassed to operate on
objects that represent files. Such objects must stringify to a file path.
The following private implementation methods must be overridden:
• _objectify -- given a path, return an object
• _children -- given a directory, return an (unsorted) list of [ basename, full path ]
entries within it, excluding "." and ".."
Note that "_children" should return a list of tuples, where the tuples are array
references containing basename and full path.
See Path::Class::Rule source for an example.
LEXICAL WARNINGS
If you run with lexical warnings enabled, "Path::Iterator::Rule" will issue warnings in
certain circumstances (such as an unreadable directory that must be skipped). To disable
these categories, put the following statement at the correct scope:
no warnings 'Path::Iterator::Rule';
PERFORMANCE
By default, "Path::Iterator::Rule" iterator options are "slow but safe". They ensure
uniqueness, return files in sorted order, and throw nice error messages if something goes
wrong.
If you want speed over safety, set these options:
%options = (
loop_safe => 0,
sorted => 0,
depthfirst => -1,
error_handler => undef
);
Alternatively, use the "iter_fast" and "all_fast" methods instead, which set these options
for you.
$iter = $rule->iter( @dirs, \%options );
$iter = $rule->iter_fast( @dirs ); # same thing
Depending on the file structure being searched, "depthfirst => -1" may or may not be a
good choice. If you have lots of nested directories and all the files at the bottom, a
depth first search might do less work or use less memory, particularly if the search will
be halted early (e.g. finding the first N matches.)
Rules will shortcut on failure, so be sure to put rules likely to fail early in a rule
chain.
Consider:
$r1 = Path::Iterator::Rule->new->name(qr/foo/)->file;
$r2 = Path::Iterator::Rule->new->file->name(qr/foo/);
If there are lots of files, but only a few containing "foo", then $r1 above will be
faster.
Rules are implemented as code references, so long chains have some overhead. Consider
testing with a custom coderef that combines several tests into one.
Consider:
$r3 = Path::Iterator::Rule->new->and( sub { -x -w -r $_ } );
$r4 = Path::Iterator::Rule->new->executable->writeable->readable;
Rule $r3 above will be much faster, not only because it stacks the file tests, but because
it requires only a single code reference.
CAVEATS
Some features are still unimplemented:
• Untainting options
• Some File::Find::Rule helpers (e.g. "grep")
• Extension class loading via "import()"
Filetest operators and stat rules are subject to the usual portability considerations.
See perlport for details.
SEE ALSO
There are many other file finding modules out there. They all have various
features/deficiencies, depending on your preferences and needs. Here is an (incomplete)
list of alternatives, with some comparison commentary.
Path::Class::Rule and IO::All::Rule are subclasses of "Path::Iterator::Rule" and operate
on Path::Class and IO::All objects, respectively. Because of this, they are substantially
slower on large directory trees than just using this module directly.
File::Find is part of the Perl core. It requires the user to write a callback function to
process each node of the search. Callbacks must use global variables to determine the
current node. It only supports depth-first search (both pre- and post-order). It supports
pre- and post-processing callbacks; the former is required for sorting files to process in
a directory. File::Find::Closures can be used to help create a callback for File::Find.
File::Find::Rule is an object-oriented wrapper around File::Find. It provides a number of
helper functions and there are many more "File::Find::Rule::*" modules on CPAN with
additional helpers. It provides an iterator interface, but precomputes all the results.
File::Next provides iterators for file, directories or "everything". It takes two
callbacks, one to match files and one to decide which directories to descend. It does not
allow control over breadth/depth order, though it does provide means to sort files for
processing within a directory. Like File::Find, it requires callbacks to use global
variables.
Path::Class::Iterator walks a directory structure with an iterator. It is implemented as
Path::Class subclasses, which adds a degree of extra complexity. It takes a single
callback to define "interesting" paths to return. The callback gets a
Path::Class::Iterator::File or Path::Class::Iterator::Dir object for evaluation.
File::Find::Object and companion File::Find::Object::Rule are like File::Find and
File::Find::Rule, but without File::Find inside. They use an iterator that does not
precompute results. They can return File::Find::Object::Result objects, which give a
subset of the utility of Path::Class objects. File::Find::Object::Rule appears to be a
literal translation of File::Find::Rule, including oddities like making "-M" into a
boolean.
File::chdir::WalkDir recursively descends a tree, calling a callback on each file. No
iterator. Supports exclusion patterns. Depth-first post-order by default, but offers
pre-order option. Does not process symlinks.
File::Find::Iterator is based on iterator patterns in Higher Order Perl. It allows a
filtering callback. Symlinks are followed automatically without infinite loop protection.
No control over order. It offers a "state file" option for resuming interrupted work.
File::Find::Declare has declarative helper rules, no iterator, is Moose-based and offers
no control over ordering or following symlinks.
File::Find::Node has no iterator, does matching via callback and offers no control over
ordering.
File::Set builds up a set of files to operate on from a list of directories to include or
exclude, with control over recursion. A callback is applied to each file (or directory)
in the set. There is no iterator. There is no control over ordering. Symlinks are not
followed. It has several extra features for checksumming the set and creating tarballs
with /bin/tar.
THANKS
Thank you to Ricardo Signes (rjbs) for inspiring me to write yet another file finder
module, for writing file finder optimization benchmarks, and tirelessly running my code
over and over to see if it got faster.
• See the speed of Perl file finders <http://rjbs.manxome.org/rubric/entry/1981>
SUPPORT
Bugs / Feature Requests
Please report any bugs or feature requests through the issue tracker at
<https://github.com/dagolden/Path-Iterator-Rule/issues>. You will be notified
automatically of any progress on your issue.
Source Code
This is open source software. The code repository is available for public review and
contribution under the terms of the license.
<https://github.com/dagolden/Path-Iterator-Rule>
git clone https://github.com/dagolden/Path-Iterator-Rule.git
AUTHOR
David Golden <dagolden@cpan.org>
CONTRIBUTORS
• David Steinbrunner <dsteinbrunner@pobox.com>
• Diab Jerius <djerius@cfa.harvard.edu>
• Edward Betts <edward@4angle.com>
• Gian Piero Carrubba <gpiero@butterfly.fdc.rm-rf.it>
• Graham Knop <haarg@cpan.org>
• Ricardo Signes <rjbs@cpan.org>
• Slaven Rezic <slaven.rezic@idealo.de>
• Toby Inkster <tobyink@cpan.org>
COPYRIGHT AND LICENSE
This software is Copyright (c) 2013 by David Golden.
This is free software, licensed under:
The Apache License, Version 2.0, January 2004