Re: opendir

[John W. Krahn]

MK wrote:

i am trying to create a perl routine to traverse directories (like a file browser) that will be incorporated into a more specific framework, but for some incomprehensible (to me) reason, opendir will not produce correct information when called in a sub!!! Why (the exact same script works fine -- once, obviously -- without the sub loop)?

#!/usr/bin/perl
# move thru directories

use warnings;

When I compile your code I get some warnings:

$ perl -c dirmenu.pl
Name "main::ND" used only once: possible typo at dirmenu.pl.tdy line 19.
Name "main::dirlist" used only once: possible typo at dirmenu.pl.tdy
line 30.
Name "main::chuck" used only once: possible typo at dirmenu.pl.tdy line 40.
dirmenu.pl syntax OK

#use strict;

You shouldn't disable the strict pragma.

use File::stat;

Based on your code, you don't really need this module.

sub listdir {
    $dir = $_[ 0 ];
    opendir( D, "$dir" );

perldoc -q quoting
Found in /usr/share/perl/5.8/pod/perlfaq4.pod
       What's wrong with always quoting "$vars"?

You should always verify system calls like opendir() completed
successfully.  You should probably also use lexically scoped directory
handles:

      opendir my $D, $dir or die "Cannot opendir '$dir' $!";

    @list = readdir( D );

      my @list = readdir $D;
      closedir $D;

    contentof();
    selecta();
    }

sub selecta {
    print "\nwhich directory (#): ";
    $new = <>;

User input from STDIN will have a trailing newline so you have to
chomp() it:

      chomp( $new = <> );

    closedir( ND );

The directory handle ND has not been opened so why are you closing it?

    listdir( $new );
    }

sub contentof {
    opendir( D, "$dir" );

perldoc -q quoting
Found in /usr/share/perl/5.8/pod/perlfaq4.pod
       What's wrong with always quoting "$vars"?

You should always verify system calls like opendir() completed
successfully.  You should probably also use lexically scoped directory
handles:

      opendir my $D, $dir or die "Cannot opendir '$dir' $!";

    @list = readdir( D );

      my @list = readdir $D ;
      closedir $D;

    $num  = 0;
    foreach $file ( @list ) {
        if ( -d $file ) {

-d looks for $file in the current directory but the file name is
actually in "$dir/$file".

            print "$num: $file\n";
            $dirlist[ $num ] = $file;
            $num++;    # increment $num

It would be simpler just to use push():

              push @dirlist, $file;

            }
        }
    }

$dir = $ARGV[ 0 ];     # stat (eg) won't deal w/ @ARGV

What makes you think that stat() won't deal with @ARGV?

print "directory $dir --\n";
contentof();
closedir( D );

You should put closedir() in the scope that it is opened instead of at
file scope.

$chuck = <>;           # deals with a strange extra stdout->stdin return

If you don't need the variable $chuck then you can just use void context:

<>;           # deals with a strange extra stdout->stdin return

selecta();

John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order.                            -- Larry Wall

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