in reply to Re: I need help with opening a directory and reading files in that directory.
in thread I need help with opening a directory and reading files in that directory.

Shadowsong, this is what I came up with. The directory is being read and information is being stored in memory, but I'm have having trouble opening the .txt files to read the data in those files. I thought I was doing it the right way by using hashes to keying a value. But, it is still not reading the data in the .txt file. Am I doing something wrong or am I still not reading what is in the file?

#!/usr/bin/perl -slw

use strict;
use warnings;
use Data::Dumper;

my %length;
my %songs;

opendir DH, "Y://perlscripts2/software/perl2/music" or die $!; # open 
+current directory
while($_ = readdir(DH)){
    # don't evaluate special dirs '.' & '..'
    next if $_ eq "." or $_ eq "..";
    if ($_ =~ /\.txt/){
        chomp $_;
        my ($artist, $song_title) = split '-', $_, 3;
        $length{$artist}{$artist} = $artist;
        $length{$artist}{$song_title} = $song_title;
    print "$_"; # print this file/directory's name
    
    }
    # as a by-product of readdir; use the file's stat info
    # to check whether this is indeed a regular file we can
    # open for reading/further processing
    if (-f $_) {
        open FH, "<$_" or die $!;
        print "output for file: $_\n";
            while (my $line = <FH>) {
                print "$line\n";
                if ($line =~ /\.txt/){
                my($album, $minutes, $seconds, $genre) = split ':', $l
+ine, 4;
                $songs{$album} = $album;
                $songs{$minutes} = $minutes;
                $songs{$seconds} = $seconds;
                $songs{$genre} = $genre;
                print $album, "\n";
                }
                close FH; 
            }   
    }
}closedir DH;

foreach my $artist ( sort keys %length )
{
    
        print "$artist is the name of the Artist\n";
        
}
foreach my $album ( sort keys %songs )
{
        print "$album is this now\n";
}

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Thanks, Brandon

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Re^3: I need help with opening a directory and reading files in that directory.
by shadowsong (Pilgrim) on Sep 08, 2015 at 22:15 UTC

    Brandon,

    Let's looks at the solution you have come up with; but before we do - just a quick note:

    #!/usr/bin/perl -slw

use strict;
use warnings;

    [download]

    The use warnings; pragma is redundant if you supply the -w switch
    --

    Now, looking at your solution we can see that you've opened a target directory and proceeded to read its contents via the excerpt below:

    opendir DH, "Y://perlscripts2/software/perl2/music" or die $!; # open 
+current directory
while($_ = readdir(DH)){
    # don't evaluate special dirs '.' & '..'
    next if $_ eq "." or $_ eq "..";

    [download]

    What comes next is a bit peculiar..

        if ($_ =~ /\.txt/){
        chomp $_;
        my ($artist, $song_title) = split '-', $_, 3;
        $length{$artist}{$artist} = $artist;
        $length{$artist}{$song_title} = $song_title;
    print "$_"; # print this file/directory's name
    
    }

    [download]

    What you're saying above is to match filenames with ".txt" in them. Are you sure this is what you want to do? Do you have ".txt" embedded within your music filenames?

    Notwithstanding your expectations of the existence of a ".txt" filename which you'd like to process in your music files directory - you should be doing that check within the 2nd if (-f $_) conditional; so you only check legitimate regular files for the ".txt" string.

    Here's a small script I wrote to process some flac files within one of my music directories (which is devoid of any ".txt" files)

    #! perl -slw
use strict;
use Data::Dumper;
$Data::Dumper::Sortkeys = 1;

my ($id,$songs_ref,$artists_ref,$albums_ref,%songs,%artists,%albums);
opendir DH, "D:/music/Alice In Chains/2001 - Greatest Hits" 
    or die $!; # open current directory
while($_ = readdir(DH)){
    # don't evaluate special dirs '.' & '..'
    next if $_ eq "." or $_ eq "..";

    # music files in this directory are *.flac files with the 
    # naming style: <track#> - <band> - <album> - <track.flac>
    # no need to check stat info - we're processing files that
    # end in .flac (notice the end-of-line match char '$'?)
    if (m{\.flac$}){ # tip: m{..} is another way of saying /../

    # add .flac to the split pattern so that it is not 
    # included in our "<track>" field
    my ($track_num, $band, $album, $track) = split / \- |\.flac/;

    # increment our hash ref id so we don't overwrite entries
    $id++;

    # -------------------------------------------------------
    # Example Using Hash References
    # -------------------------------------------------------
    $songs_ref->{$id}->{TITLE}        = $track;
    $songs_ref->{$id}->{ARTIST}       = $band;
    $songs_ref->{$id}->{FAVOURITE}    = 1 if $track eq 'Would';
    $songs_ref->{$id}->{TRACK_LENGTH} = undef; # to do later

    $artists_ref->{$id}->{NAME}           = $band;
    $artists_ref->{$id}->{SONGS}->{TITLE} = $track;
    $artists_ref->{$id}->{SONGS}->{ALBUM} = $album;

    $albums_ref->{$id}->{ARTIST}             = $band;
    $albums_ref->{$id}->{NAME}               = $album;
    $albums_ref->{$id}->{SONGS}->{TITLE}     = $track;
    $albums_ref->{$id}->{SONGS}->{TRACK_NUM} = $track_num;

    # -------------------------------------------------------
    # Example Using Hashes
    # -------------------------------------------------------
    $songs{$id}{TITLE}        = $track;
    $songs{$id}{ARTIST}       = $band;
    $songs{$id}{TRACK_LENGTH} = undef; # to do later

    $artists{$id}{NAME}         = $band;
    $artists{$id}{SONGS}{TITLE} = $track;
    $artists{$id}{SONGS}{ALBUM} = $album;

    $albums{$id}{ARTIST}           = $band;
    $albums{$id}{NAME}             = $album;
    $albums{$id}{SONGS}{TITLE}     = $track;
    $albums{$id}{SONGS}{TRACK_NUM} = $track_num;
    }
}
closedir DH;

# use perl's object data serializer to view our data
print Dumper $songs_ref;
print Dumper $artists_ref;
print Dumper $albums_ref;

print Dumper \%songs;
print Dumper \%artists;
print Dumper \%albums;
__END__

    [download]

    I would like to focus on why it is you're not getting those ".txt" files open for processing, but to do that we need to establish which files are in the directory that you're reading from? Have a look at the example provided and if you find it's still necessary to open and read some kind of ".txt" file - please provide us with the output of dir "Y://perlscripts2/software/perl2/music"

    Good luck!

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      Shadowsong, here is the output of my directory. I know that music files don't consist of .txt extensions, but this is what I was asked to do for the assignment. So, I made these files names up and went with this type. Inside the files there is supposed to one line that contains the album, minutes, seconds, and genre each separate by ":". The Sun and the Moon:3:47:Alternative

      OUTPUT of DIRECTORY:<\p>

      The Bravery-Believe.txt

      output for file: The Bravery-Believe.txt

      The Bouncing Souls-True Believers.txt

      output for file: The Bouncing Souls-True Believers.txt

      The Kickdrums-Atonement.txt

      output for file: The Kickdrums-Atonement.txt

      I'm assuming that this:

      if ($_ =~ /\.txt/){
        chomp $_;
        my ($artist, $song_title) = split '-', $_, 3;
        $length{$artist}{$artist} = $artist;
        $length{$artist}{$song_title} = $song_title;
    print "$_"; # print this file/directory's name

      [download]

      Could be part of this: 

      open FH, "<$_" or die $!;
    print "output for file: $_\n";
    while (my $line = <FH>) {
        print $line;
        chomp $line;
        if ($line =~ /\.txt/){
    my $artist;
my ($album, $minutes, $seconds, $genre) = split ':', $line, 4;
        $length{$artist}{album} = $album;
        $length{$artist}{minutes} = $minutes;
        $length{$artist}{seconds} = $seconds;
        $length{$artist}{genre} = $genre;
        print $album, "\n";
        }

      [download]

      So, I'm still trying to open the FH of the .txt file and read the contents to get the total amount of the song length for each line and print it out. "Saying this Artist has a total amount of Music". I really appreciate your guidance and patience with me. I know I am a newby at this, but I'm willing to put the time in to learn and get the most out of this language. Thanks, Brandon

[reply]
[d/l]
[select]

        Ahh, now I see what you're trying to do...

        Remember when we warned things could get hairy? OK, firstly - please consider what Anonymous Monk said very carefully..

        OK, now that we know what your files look like, lets focus on why we're not opening/processing them. 2 things:

        • Are the files being tested accessible to the script? i.e. does the script live in the same directory as they do? Y://perlscripts2/software/perl2/music. If it doesn't - you'll need to consider how to supply your if (-f ...) conditional with the absolute path to the file you're testing OR change directory to the same directory as the files you're testing prior to testing them (see chdir)
        • Once you've addressed the incorrectly placed close FH function call - mentioned by Anonymous Monk above (i.e. move it out of your while loop so you don't close a filehandle while working with it), I'd like you to reassess where you'd planned to put the if (/\.txt$/) conditional. hint: should we be testing a file after opening it?

        Have another crack at it and see what you come up with. Larry Wall said that Perl is an empirical science - you learn things about it by trying it out.

        Keep up the good work!

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Re^3: I need help with opening a directory and reading files in that directory.
by Anonymous Monk on Sep 08, 2015 at 23:03 UTC 

    opendir DH, "Y://perlscripts2/software/perl2/music" or die $!;
while($_ = readdir(DH)){
    ...
    if (-f $_) {

    [download]

    The file test will work when the value being tested is a path which can be accessed from the current directory where the program was started. As is, $_ contains only the bare file name, devoid of directory name. 

            open FH, "<$_" or die $!;
        print "output for file: $_\n";
            while (my $line = <FH>) {
                                ...
                if ($line =~ /\.txt/){
                                  ...
                }
                close FH; 
            }

    [download]

    A closure of the file handle while still iterating over it will result in "readline() on closed filehandle" (perl 5.16.2) error message, causing premature demise of the program. If the file handle needs to be closed early, then should skip the whole loop via last.

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