Next(3)

NAME
File::Next - File-finding iterator

VERSION
Version 1.18

SYNOPSIS
File::Next is a lightweight, taint-safe file-finding module. It has no non-core prerequisites.

    use File::Next;

    my $files = File::Next::files( '/tmp' );

    while ( defined ( my $file = $files->() ) ) {
        # do something...
    }

OPERATIONAL THEORY
The two major functions, files() and dirs(), return an iterator that will walk through a directory tree. The simplest use case is:

    use File::Next;

    my $iter = File::Next::files( '/tmp' );

    while ( defined ( my $file = $iter->() ) ) {
        print $file, "\n";
    }

    # Prints...
    /tmp/foo.txt
    /tmp/bar.pl
    /tmp/baz/1
    /tmp/baz/2.txt
    /tmp/baz/wango/tango/purple.txt

Note that only files are returned by files()'s iterator. Directories are ignored.

In list context, the iterator returns a list containing $dir, $file and $fullpath, where $fullpath is what would get returned in scalar context.

The first parameter to any of the iterator factory functions may be a hashref of options.

ITERATORS
For the three iterators, the \%options are optional.

  files( [ \%options, ] @starting_points )
Returns an iterator that walks directories starting with the items in @starting_points. Each call to the iterator returns another regular file.

  dirs( [ \%options, ] @starting_points )
Returns an iterator that walks directories starting with the items in @starting_points. Each call to the iterator returns another directory.

  everything( [ \%options, ] @starting_points )
Returns an iterator that walks directories starting with the items in @starting_points. Each call to the iterator returns another file, whether it's a regular file, directory, symlink, socket, or whatever.

  from_file( [ \%options, ] $filename )
Returns an iterator that iterates over each of the files specified in $filename. If $filename is "-", then the files are read from STDIN.

The files are assumed to be in the file one filename per line. If $nul_separated is passed, then the files are assumed to be NUL-separated, as by "find -print0".

If there are blank lines or empty filenames in the input stream, they are ignored.

Each filename is checked to see that it is a regular file or a named pipe. If the file does not exists or is a directory, then a warning is thrown to warning_handler, and the file is skipped.

The following options have no effect in "from_files": descend_filter, sort_files, follow_symlinks.

SUPPORT FUNCTIONS

  sort_standard( $a, $b )
A sort function for passing as a "sort_files" option:

    my $iter = File::Next::files( {
        sort_files => \&File::Next::sort_standard,
    }, 't/swamp' );

This function is the default, so the code above is identical to:

    my $iter = File::Next::files( {
        sort_files => 1,
    }, 't/swamp' );

  sort_reverse( $a, $b )
Same as "sort_standard", but in reverse.

  reslash( $path )
Takes a path with all forward slashes and rebuilds it with whatever is appropriate for the platform. For example 'foo/bar/bat' will become 'foo\bar\bat' on Windows.

This is really just a convenience function. I'd make it private, but ack wants it, too.

CONSTRUCTOR PARAMETERS

  file_filter -> \&file_filter
The file_filter lets you check to see if it's really a file you want to get back. If the file_filter returns a true value, the file will be returned; if false, it will be skipped.

The file_filter function takes no arguments but rather does its work through a collection of variables.

•   $_ is the current filename within that directory

•   $File::Next::dir is the current directory name

•   $File::Next::name is the complete pathname to the file

These are analogous to the same variables in File::Find.

    my $iter = File::Next::files( { file_filter => sub { /\.txt$/ } }, '/tmp' );

By default, the file_filter is "sub {1}", or "all files".

This filter has no effect if your iterator is only returning directories.

  descend_filter => \&descend_filter
The descend_filter lets you check to see if the iterator should descend into a given directory. Maybe you want to skip CVS and .svn directories.

    my $descend_filter = sub { $_ ne "CVS" && $_ ne ".svn" }

The descend_filter function takes no arguments but rather does its work through a collection of variables.

•   $_ is the current filename of the directory

•   $File::Next::dir is the complete directory name

The descend filter is NOT applied to any directory names specified as @starting_points in the constructor. For example,

    my $iter = File::Next::files( { descend_filter => sub{0} }, '/tmp' );

always descends into /tmp, as you would expect.

By default, the descend_filter is "sub {1}", or "always descend".

  error_handler => \&error_handler
If error_handler is set, then any errors will be sent through it. If the error is OS-related (ex. file not found, not permissions), the native error code is passed as a second argument. By default, this value is "CORE::die". This function must NOT return.

  warning_handler => \&warning_handler
If warning_handler is set, then any errors will be sent through it. By default, this value is "CORE::warn". Unlike the error_handler, this function must return.

  sort_files => [ 0 | 1 | \&sort_sub]
If you want files sorted, pass in some true value, as in "sort_files => 1".

If you want a special sort order, pass in a sort function like "sort_files => sub { $a->[1] cmp $b->[1] }". Note that the parms passed in to the sub are arrayrefs, where $a->[0] is the directory name, $a->[1] is the file name and $a->[2] is the full path. Typically you're going to be sorting on $a->[2].

  follow_symlinks => [ 0 | 1 ]
If set to false, the iterator will ignore any files and directories that are actually symlinks. This has no effect on non-Unixy systems such as Windows. By default, this is true.

Note that this filter does not apply to any of the @starting_points passed in to the constructor.

You should not set "follow_symlinks => 0" unless you specifically need that behavior. Setting "follow_symlinks => 0" can be a speed hit, because File::Next must check to see if the file or directory you're about to follow is actually a symlink.

  nul_separated => [ 0 | 1 ]
Used by the "from_file" iterator. Specifies that the files listed in the input file are separated by NUL characters, as from the "find" command with the "-print0" argument.

PRIVATE FUNCTIONS

  _setup( $default_parms, @whatever_was_passed_to_files() )
Handles all the scut-work for setting up the parms passed in.

Returns a hashref of operational options, combined between $passed_parms and $defaults, plus the queue.

The queue prep stuff takes the strings in @starting_points and puts them in the format that queue needs.

The @queue that gets passed around is an array, with each entry an arrayref of $dir, $file and $fullpath.

  _candidate_files( $parms, $dir )
Pulls out the files/dirs that might be worth looking into in $dir. If $dir is the empty string, then search the current directory.

$parms is the hashref of parms passed into File::Next constructor.

DIAGNOSTICS

"File::Next::files must not be invoked as File::Next->files"
"File::Next::dirs must not be invoked as File::Next->dirs"
"File::Next::everything must not be invoked as File::Next->everything"

The interface functions do not allow for the method invocation syntax and throw errors with the messages above. You can work around this limitation with "can" in UNIVERSAL.

    for my $file_system_feature (qw(dirs files)) {
        my $iterator = File::Next->can($file_system_feature)->($options, $target_directory);
        while (defined(my $name = $iterator->())) {
            # ...
        }
    }

SPEED TWEAKS

•   Don't set "follow_symlinks => 0" unless you need it.

AUTHOR
Andy Lester, "<andy at petdance.com>"

BUGS
Please report any bugs or feature requests to <http://github.com/petdance/file-next/issues>.

Note that File::Next does NOT use <http://rt.cpan.org> for bug tracking.

SUPPORT
You can find documentation for this module with the perldoc command.

    perldoc File::Next

You can also look for information at:

•   File::Next's bug queue

    <http://github.com/petdance/file-next/issues>

•   CPAN Ratings

    <http://cpanratings.perl.org/d/File-Next>

•   Search CPAN

    <http://search.cpan.org/dist/File-Next>

•   Source code repository

    <http://github.com/petdance/file-next/tree/master>

ACKNOWLEDGEMENTS
All file-finding in this module is adapted from Mark Jason Dominus' marvelous Higher Order Perl, page 126.

Thanks to these fine contributors: Varadinsky, Paulo Custodio, Gerhard Poul, Brian Fraser, Todd Rinaldo, Bruce Woodward, Christopher J. Madsen, Bernhard Fisseni and Rob Hoelz.

COPYRIGHT & LICENSE
Copyright 2005-2017 Andy Lester.

This program is free software; you can redistribute it and/or modify it under the terms of the Artistic License version 2.0.