unable to parse json

[somequery]

I am parsing the json file:
{
"default_txt": "sometext"
}

C++ code:
std::ifstream jsonFile("appTest.json", std::ios::in);
nlohmann::json parsed_json = nlohmann::json::parse(jsonFile);

I get an error:
terminate called after throwing an instance of 'nlohmann::detail::parse_error'
what(): [json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal

I tried:
1/ full path name instead of just the file name
2/ I have checked the json formatting in online parsers with success
3/ parsed successfully with boost property tree

Do yo have any suggestions?

Thanks.

[gregmarr]

Have you tried printing out the text after opening the stream? You appear to have some sort of garbage before the first character.

[somequery]

It prints fine: std::cout << jsonFile.rdbuf() << std::endl;

[nlohmann]

Could you please share the file?

[somequery]

I have attached the file (I changed the extension from json to txt).
Thanks.
appTest.txt

[nlohmann]

Hm. This all looks good:

#include "json.hpp"
#include <iostream>
#include <fstream>

using json = nlohmann::json;

int main() {
    std::ifstream f("/Users/niels/Downloads/appTest.txt");
    json j = json::parse(f);
    std::cout << j << std::endl;
}

produces

{"default":"sometext"}

[nlohmann]

@somequery Can you try the exact program of #1525 (comment) (well, with a different path...)?

[somequery]

I used the full path as you mentioned, but the result is the same. I run it from VS and from a command line also, from the directory containing both the out and json file. I've received the same error always.

[somequery]

After rebuilding it now works. But there is still problem (with the same error) on nlohmann::json parsed_json = nlohmann::json::parse(f);

Am I doing wrong something?

[nlohmann]

After rebuilding it now works.

Does it mean you can parse the file successfully now?

But there is still problem (with the same error) on nlohmann::json parsed_json = nlohmann::json::parse(f);

What is the problem?

[somequery]

Does it mean you can parse the file successfully now?
Yes. The json file has to be specified with full path. In my case "./appTest.json"

What is the problem?
while learning the API I was using both:
std::ifstream jsonFile(./appTest.json);
nlohmann::json parsed_json = nlohmann::json::parse(jsonFile);

and

nlohmann::json jFields;
jsonFile >> jFields;

I figured out that I should be using the first or the second way but not both together. So everything works now.

Thanks.

[nlohmann]

Thanks for clarifying!

[terzioglan]

Hi,

I'm having parse_error.101 as well. I went through a bunch of reported issues about this but none of the suggested solutions seem to have solve my issue: I checked the encoding and made sure it's UTF8, I tried to use the full file path, I checked the bytes with Bless hex editor and everything seems to be in place.

Here is the exact program I'm using:

#include <iostream>
#include <fstream>
#include <nlohmann/json.hpp>

int main(int argc, char **argv)
{
  std::string line; 
  std::ifstream myJsonFile("/home/terzi/rosSpace/src/cirakdevel/cirakJson/example_1.json");

  if (myJsonFile.is_open())
  {
    while ( getline (myJsonFile,line) )
    {
      std::cout << line << '\n';
    }
    // myJsonFile.close();
  }
  else std::cout << "Unable to open file"; 

  try
  {
    // parsing input with a syntax error
    nlohmann::json::parse(myJsonFile);
  }
  catch (nlohmann::json::parse_error& e)
  {
    // output exception information
    std::cout << "message: " << e.what() << '\n'
              << "exception id: " << e.id << '\n'
              << "byte position of error: " << e.byte << std::endl;
  }
  return 0;
}

This is the .json file I'm using with its extension modified to .txt: example_1.txt

Here is the output of the program:

{
    "fruit": "Apple",
    "size": "Large",
    "color": "Red"
}
message: [json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal
exception id: 101
byte position of error: 1

I'm working on Ubuntu 16.04, compiling in a Catkin workspace.

[gregmarr]

You read the entire file and print it out, so there's nothing left to parse in the stream. What happens if you don't do that read and print first?

[terzioglan]

Thanks for the tip @gregmarr ! You are right and this actually solved the issue!.. Much kudos!

[gregmarr]

You're welcome.