-s file test operator only works in same directory

Bowlslaw has asked for the wisdom of the Perl Monks concerning the following question:

Hello, I have made a perl script which takes the files from a directory listed on the command line and places them into an array of hashes with key/value pairs path:full path to file, size:size of file in bytes, and id:sha256sum of file. It works fine when I use its own directory, but it returns "undef" on the id value when used in other directories, and the $! error is "no such directory or file found", which I find quite odd considering that it lists the filenames sha256sums just fine.

use strict;
use warnings;
use Data::Dumper qw(Dumper);
use File::Spec;
use Digest::SHA qw(sha256_hex);

print join("\n", @ARGV),"\n\n";
#print Dumper \@ARGV;

my $dir = $ARGV[0];
my $url = $ARGV[1];

my @array;
opendir DIR, $dir or die "cannot open dir $dir: $!";
while(my $file = readdir DIR) {
    next unless(-f "${\File::Spec->catfile($dir, $file)}");
    next if("$file" =~ m/^\./);
    print "${\File::Spec->rel2abs($file)}\n";

    my %hash = (
        path    =>  File::Spec->rel2abs($file),
        size    =>  -s $file,
        id      =>  sha256_hex($file),
    );

    push(@array, \%hash);
}
closedir DIR;

print Dumper sort \@array;
[download]

Comment on -s file test operator only works in same directory Download Code

Replies are listed 'Best First'.
Re: -s file test operator only works in same directory by NetWallah (Canon) on Dec 08, 2017 at 02:12 UTC
$file contains the relative path (No directory name). Early in your loop, you should probably update that to the full path : `$file = File::Spec->catfile($dir, $file);` [download] ALso - Why are you using the strange "${\File::Spec...}" syntax ? All power corrupts, but we need electricity.	[reply] [d/l]
Re^2: -s file test operator only works in same directory by Bowlslaw (Acolyte) on Dec 08, 2017 at 03:31 UTC
Because subrefs are cool?	[reply]
Re^3: -s file test operator only works in same directory by NetWallah (Canon) on Dec 08, 2017 at 05:41 UTC
That is not a subref. `perl -E ' say ${\"FFF"}' FFF` [download] All you are doing is referencing then de-referencing the returned value of the sub. It is just a way to call a sub inside quotes - but I dislike the obfuscation it causes. All power corrupts, but we need electricity.	[reply] [d/l]
Re^4: -s file test operator only works in same directory by Bowlslaw (Acolyte) on Dec 08, 2017 at 13:00 UTC
Re: -s file test operator only works in same directory by Dallaylaen (Chaplain) on Dec 08, 2017 at 07:54 UTC
You are calling `-f` on full file name, yet `-s` on just the base name, hence the discrepancy. I would just cache the full name once and for all (well, until next loop iteration). Something like this: `while(my $file = readdir DIR) { next if $file =~ /^./; # still working with name only $file = File::Spec->catfile( $dir, $file ); next unless -f $file; # working with full path from now on # ....... proceed with the rest of loop };` [download]	[reply] [d/l]
Re: -s file test operator only works in same directory by dbuckhal (Chaplain) on Dec 08, 2017 at 03:22 UTC
One thing that has helped me in similar situations was to change into the directory containing the files of interest. For example, note the tiny changes to your code: use strict; use warnings; use Data::Dumper qw(Dumper); use File::Spec; use Digest::SHA qw(sha256_hex); print join("\n", @ARGV),"\n\n"; #print Dumper \@ARGV; my $dir = $ARGV[0]; my $url = $ARGV[1]; my @array; opendir DIR, $dir or die "cannot open dir $dir: $!"; chdir $dir; # added chdir while(my $file = readdir DIR) { next unless -f $file; # simplified fil +e check next if($file =~ m/^\./); # removed quotes print "${\File::Spec->rel2abs($file)}\n"; my %hash = ( path => File::Spec->rel2abs($file), size => -s $file, id => sha256_hex($file), ); push(@array, \%hash); } closedir DIR; print Dumper sort \@array; [download] Hope it works out for you! --Derrick	[reply] [d/l]
Re: -s file test operator only works in same directory by hippo (Archbishop) on Dec 08, 2017 at 09:16 UTC
Here is the simple refutation of that assertion. `use strict; use warnings; use Cwd; use Test::More tests => 2; isnt (getcwd, '/etc', 'Not in /etc/'); cmp_ok (-s '/etc/fstab', '>', 0, '-s /etc/fstab is positive');` [download] The reason is that given by my speedier brethren: namely absolute versus relative paths.	[reply] [d/l]