Re^3: failing to use getdents system call on Linux

Oh yes, infinite loop is a problem here, since I'm getting 1 or zero from $len. Here is the updated code:

#!/usr/bin/env perl
use warnings;
use strict;
use File::Spec;
use Getopt::Std;
use Fcntl;
use constant BUF_SIZE => 1024 * 1024 * 5;
require 'syscall.ph';

my %opts;

getopts( 'd:', \%opts );

die 'option -d <DIRECTORY> is required'
  unless ( ( exists( $opts{d} ) ) and ( defined( $opts{d} ) ) );

sysopen( my $fd, $opts{d}, O_RDONLY | O_DIRECTORY );
open( my $out, '>:raw', 'perldata.bin' ) or die $!;

while (1) {

    my $buf = "\0" x BUF_SIZE;
    my $read = syscall( &SYS_getdents, fileno($fd), $buf, BUF_SIZE );

    if ( ( $read == -1 ) and ( $! != 0 ) ) {
        die "failed to syscal getdents: $!";
    }

    print $out($buf);
    close($out);
    last;

=pod
    last if ( $read == 0 );

    while ( $read != 0 ) {
        my ( $ino, $off, $len, $name ) = unpack( "LLSZ*", $buf );

        unless ( ( $name eq '.' ) or ( $name eq '..' ) ) {
            my $path = File::Spec->catfile( $opts{d}, $name );
            print $path,"\n";
        }
        substr( $buf, 0, $len ) = '';
        $read -= $len;
    }
=cut

}
[download]

The part changed to Pod is exactly the one that put me in a "infinite" loop (probably not infinite, but long enough to create a very large file, but I killed the process once it reached GB).

As you can see in the code, I used the same buffer size as in the C code... but results are the same:

[me@localhost ~]$ echo 'C output'; head hardlist.txt; echo 'Perl outpu
+t'; head perldata.txt 
C output
00000000  42 ed 09 00 00 00 00 00  01 00 00 00 00 00 00 00  |B........
+.......|
00000010  18 00 2e 00 00 00 00 04  e2 6c 08 00 00 00 00 00  |.........
+l......|
00000020  0d 8e 0e 00 00 00 00 00  18 00 2e 2e 00 00 00 04  |.........
+.......|
00000030  cb ed 09 00 00 00 00 00  a1 07 1e 00 00 00 00 00  |.........
+.......|
00000040  e2 6c 08 00 00 00 00 00  0d 8e 0e 00 00 00 00 00  |.l.......
+.......|
00000050  18 00 2e 2e 00 00 00 04  cb ed 09 00 00 00 00 00  |.........
+.......|
00000060  a1 07 1e 00 00 00 00 00  20 00 78 61 61 61 61 61  |........ 
+.xaaaaa|
00000070  61 61 61 66 66 00 00 08  54 f0 09 00 00 00 00 00  |aaaff...T
+.......|
00000080  cb ed 09 00 00 00 00 00  a1 07 1e 00 00 00 00 00  |.........
+.......|
00000090  20 00 78 61 61 61 61 61  61 61 61 66 66 00 00 08  | .xaaaaaa
+aaff...|
Perl output
00000000  42 ed 09 00 00 00 00 00  01 00 00 00 00 00 00 00  |B........
+.......|
00000010  18 00 2e 00 00 00 00 04  e2 6c 08 00 00 00 00 00  |.........
+l......|
00000020  0d 8e 0e 00 00 00 00 00  18 00 2e 2e 00 00 00 04  |.........
+.......|
00000030  cb ed 09 00 00 00 00 00  a1 07 1e 00 00 00 00 00  |.........
+.......|
00000040  20 00 78 61 61 61 61 61  61 61 61 66 66 00 00 08  | .xaaaaaa
+aaff...|
00000050  54 f0 09 00 00 00 00 00  f3 a6 28 00 00 00 00 00  |T........
+.(.....|
00000060  20 00 78 61 61 61 61 61  61 61 62 64 75 00 00 08  | .xaaaaaa
+abdu...|
00000070  f7 f0 09 00 00 00 00 00  c8 13 67 00 00 00 00 00  |.........
+.g.....|
00000080  20 00 78 61 61 61 61 61  61 61 62 6a 77 00 00 08  | .xaaaaaa
+abjw...|
00000090  c5 ee 09 00 00 00 00 00  6e 5c 6d 00 00 00 00 00  |........n
+\m.....|
[download]

Alceu Rodrigues de Freitas Junior
---------------------------------
"You have enemies? Good. That means you've stood up for something, sometime in your life." - Sir Winston Churchill

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