Question 174899 in Json Question posted in
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Is there an error using my $json_data = decode_json(<$fh>)?

I am trying to run a simple Perl JSON example with the JSON Perl module
and can’t find the issues with line:

my $json_data = decode_json(<$fh>);

I get the following error. Any help would be appreciated.

Susan@Kona MINGW64 /c/data/data/data/quickPerlTest
$ perl test.pl
, or } expected while parsing object/hash, at character offset 3 (before "(end of string)") at test.pl line 9.

use JSON;

# open the json file
my $json_file = 'example_json.json';

open(my $fh, '<', $json_file) or die "Could not open file '$json_file' $!";

# decode the json file  
my $json_data = decode_json(<$fh>);

# access the elements of the json file
foreach my $item ( @{$json_data->{items}} ) {
    print "ID: $item->{id}n";
    print "Title: $item->{title}n";
}

Susan@Kona MINGW64 /c/data/data/data/quickPerlTest
$ cat example_json.json
{
  "glossary": {
    "title": "example glossary",
    "GlossDiv": {
      "title": "S",
      "GlossList": {
        "GlossEntry": {
          "ID": "SGML",
          "SortAs": "SGML",
          "GlossTerm": "Standard Generalized Markup Language",
          "Acronym": "SGML",
          "Abbrev": "ISO 8879:1986",
          "GlossDef": {
            "para": "A meta-markup language.",
            "GlossSeeAlso": [ "GML", "XML" ]
          },
          "GlossSee": "markup"
        }
      }
    }
  }
}

Susan@Kona MINGW64 /c/data/data/data/quickPerlTest
$ perl --version | grep version
This is perl 5, version 36, subversion 0 (v5.36.0) built for x86_64-msys-thread-multi
Tags:

2

Answers


  1. 0

    The input to the decode_json function must be a string, but you are trying to pass something else to it.

    Since you already opened the file, you can slurp it into a string, then pass that to the function:

    use warnings;
use strict;
use JSON;
use Data::Dumper qw(Dumper);

# open the json file
my $json_file = 'example_json.json';

open(my $fh, '<', $json_file) or die "Could not open file '$json_file' $!";
my $string = do { local($/); <$fh> };
close $fh;

# decode the json file  
my $json_data = decode_json($string);

print Dumper($json_data);
print "ID: $json_data->{glossary}{GlossDiv}{GlossList}{GlossEntry}{ID}n";

    Look at the data structure that Dumper outputs. Your foreach loop won’t work on it.

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  2. 0

    <$fh> grabs just one line…your file appears to contain many lines so you probably want to be calling it like

    my $json_data = decode_json(join("",<$fh>));

    which will merge all the lines into one string and then pass it to the function to decode it

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