malformed JSON string in Perl

Question

I am trying to convert json file to xml. So JSON directory is scanned and if any file that arrives there will be converted to xml and moved to xml directory.

But I am getting this error

readline() on closed filehandle $fh at json.pl line 29.
Malformed JSON string, neither array, object, number, string or atom, at character offset 0 (before "(end of string)") at json.pl line 34

json.pl

#!/usr/bin/perl

use strict;
use warnings;
use File::Copy;

binmode STDOUT, ":utf8";
use utf8;

use JSON;
use XML::Simple;

# Define input and output directories
my $indir = 'json';
my $outdir = 'xml';

# Read input directory
opendir DIR, $indir or die "Failed to open $indir";
my @files = readdir(DIR);
closedir DIR;

# Read input file in json format
for my $file (@files) 
{
my $json;
{
    local $/; #Enable 'slurp' mode
    open my $fh, "<", "$indir/$file";
    $json = <$fh>;
    close $fh;
}

# Convert JSON format to perl structures
my $data = decode_json($json);

# Output as XML
open OUTPUT, '>', "$outdir/$file" or die "Can't create filehandle: $!";
select OUTPUT; $| = 1;
print "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n";
print XMLout($data);
print "\n" ;
close(OUTPUT);
unlink "$indir/$file";

}

example.json

{
"Manager":
    {
        "Name" : "Mike",
        "Age": 28,
        "Hobbies": ["Music"]
     },
"employees":
    [
        {
            "Name" : "Helen",
            "Age": 26,
            "Hobbies": ["Movies", "Tennis"]
           },
        {
            "Name" : "Rich",
            "Age": 31,
            "Hobbies": ["Football"]

        }
    ]
}

cjm · Accepted Answer · 2015-01-08 22:04:29Z

4

You aren't checking for errors during open, and you aren't skipping directory entries (readdir will return . and .. entries).

If you use

open my $fh, "<", "$indir/$file" or die "$file: $!";

you'll probably find the problem quickly.

"readline() on closed filehandle $fh" is saying "open $fh failed but you kept going anyway".

edited Jan 8, 2015 at 22:04

answered Jan 8, 2015 at 21:57

cjm

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Comments

Borodin · Accepted Answer · 2015-01-08 22:49:53Z

0

As @cjm has pointed out, the problem is that you are trying to open and read directories as well as files from your source directory.

This is a fix for that, and it also uses autodie to avoid constantly checking the status of all the IO operations. I've also tidied things up a bit.

#!/usr/bin/perl

use utf8;
use strict;
use warnings;
use autodie;

use open qw/ :std :encoding(utf8) /;

use JSON qw/ decode_json /;
use XML::Simple qw/ XMLout /;

my ($indir, $outdir) = qw/ json xml /;

my @indir = do {
  opendir my $dh, $indir;
  readdir $dh;
};

for my $file (@indir) {

  my $infile = "$indir/$file";
  next unless -f $infile;

  my $json = do {
    open my $fh, '<', $infile;
    local $/;
    <$fh>;
  };

  my $data = decode_json($json);

  my $outfile = "$outdir/$file";
  open my $out_fh, '>', "$outdir/$file";
  print $out_fh '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>', "\n";
  print $out_fh XMLout($data), "\n";
  close $out_fh;

  unlink $infile;
}

answered Jan 8, 2015 at 22:49

Borodin

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1 Comment

David W. Over a year ago

Would it be good to put a eval around the decode_json in order to handle failures? decode_json croaks on errors.

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