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    }

    if ( $stderr ) {
        warn "Warning from external command: $stderr";
    }

    return $self->_split_on_newlines( $stdout );
}

sub _split_on_newlines {
    my $self = shift;
    my $rv = shift;

    $rv =~ s{ \A \s+    }{}xms;
    $rv =~ s{    \s+ \z }{}xms;

    return split m{ \n+ }xms, $rv;
}

sub _log {
    my $self = shift;
    return if ! $self->enable_log;
    my($level, $tmpl, @param) = @_;
    my $msg = sprintf "[%s] %s\n", uc $level, $tmpl;
    printf STDERR $msg, @param;
}

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Hadoop::HDFS::Command

=head1 VERSION

version 0.007

=head1 SYNOPSIS

    use Hadoop::HDFS::Command;
    my $hdfs = Hadoop::HDFS::Command->new;
    my @rv = $hdfs->$command( @command_args );

=head1 DESCRIPTION

This is a simple wrapper around the hdfs commandline to make them easier to
call from Perl and parse their output.

The interface is partially done at the moment (see the implemented wrappers
down below).

You can always use the WebHDFS to do similar operations instead of failling
back to the commandline. However there are several benefits of using the
cli; i) you'll end up with a single C<JVM> invocation, so the response
might be faster ii) Some functionality / endpoints might be buggy for WebHDFS
but might work with the cli (for example escaping certain values is broken
in some versions, but works with the cli).

=head1 NAME

Hadoop::HDFS::Command - Wrappers for various hadoop hdfs cli commands

=head1 METHODS

=head2 new

The constructor. Available attributes are listed below.

=head3 cmd_hdfs

Default value is C</usr/bin/hdfs>. This option needs to be altered if you have
the C<`hdfs`> command in some other place.

=head3 enable_log :Bool

Can be used to enable the internal logging feature. Disabled by default.

=head2 dfs

One of the top level commands, including an interface to the sub-commands
listed below. The calling convention of the sub commands is as simple as:

    my @rv = $hdfs->dfs( \%options, $sub_command => @subcommand_args );
    # options hash is optional
    my @rv = $hdfs->dfs( $sub_command => @subcommand_args );

Available options are listed below:

=over 4

=item ignore_fail :Bool

Global.

=item silent :Bool

Global.

=item want_epoch :Bool

Only used for C<ls>. Converts timestamps to epoch.

=item callback :CODE

Only used for C<ls>. The callback always needs to return true to continue
processing, returning false from it will short-circuit the processor.

=back

=head3 du

The C<@subcommand_args> can have these defined: C<-s>, C<-h>.

    my @rv = $hdfs->dfs( du => @subcommand_args => $hdfs_path );
    my @rv = $hdfs->dfs( du => qw( -h -s ) => "/tmp" );