CODEWITHSUNDEEP
cjsoncurllibcurl
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Reputation: 14448

malformed JSON string error in C

I am sending JSON string in JSON format using curl to post JSON data.

I've used following curl command:

curl -H "Content-Type: application/json" -d '{ "Mode":"Auto","Type":"Single","IP":"9.9.9.9","FirmwarePath":""}' http://1.1.1.1/cgi-bin/update_firmware.cgi

Output of the above command:

<h1>{ "Mode":"Auto","Type":"Single","IP":"9.9.9.9","FirmwarePath":""} </h1><h1>Check Mode</h1><h1>Auto</h1><h1>Single</h1><h1 /><h1>Here Mode</h1><h1>{ "Mode":"Auto","Type":"Single","IP":"9.9.9.9","FirmwarePath":""}</h1><h1>Check Input</h1><h1>Inside Firmware updates</h1><h1>In CheckFirmware</h1><h1>curl -s --digest --basic -u root:UOIYTm7Aw52Z "http://9.9.9.9/axis-cgi/operator/param.cgi?action=list&group=Properties.Firmware.Version" | cut -d'=' -f2</h1><h1>cam Firm:5.50.4.2
</h1><h1>DB Firm: </h1>Status: 200
Content-Type: application/json; charset=ISO-8859-1

{"ReqStatus":{"Status":"Firmware is upto date or Firmaware update mode is off.","IP":null}}

So, it works fine & gives me an expected output.

Now I want this output stored in text file. So, I've made C program to achieve that:

#include <stdio.h>
#include <curl/curl.h>

size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written = fwrite(ptr, size, nmemb, stream);
    return written;
}

int main(void) {
    CURL *curl;

    FILE *fp = fopen("request.txt","w");
    CURLcode res;

    curl = curl_easy_init();

    char* jsonObj = "{\"Mode\":\"Auto\",\"type\":\"Single\",\"IP\":\"9.9.9.9\",\"FirmwarePath\":\"""\"}";
    puts(jsonObj);
    struct curl_slist *headers = NULL;
    curl_slist_append(headers, "Accept: application/json");
    curl_slist_append(headers, "Content-Type: application/json");
    curl_slist_append(headers, "charsets: utf-8");

    curl_easy_setopt(curl, CURLOPT_URL, "http://1.1.1.1/cgi-bin/update_firmware.cgi");

    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, jsonObj);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION,write_data);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA,fp);

    res = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
    return res;
}

But after executing this C program when I open request.txt file I see unexpected output.

Contents of request.txt file:

<h1>Software error:</h1>

malformed JSON string, neither array, object, number, string or atom, at character offset 0 (before "(end of string)") at /var/www/cgi-bin/update_firmware.cgi line 496

<p>
For help, please send mail to the webmaster (<a href="mailto:root@localhost">root@localhost</a>), giving this error message 
and the time and date of the error.

</p>

JSON data that I want to send is:

{  
   "Mode":"Auto",
   "Type":"Single",
   "IP":"9.9.9.9",
   "FirmwarePath":"" 
}

What I am doing wrong here ?

Upvotes: 1

Views: 212

Answers (1)

Daniel Stenberg
Daniel Stenberg

Reputation: 58234

curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");

Remove that option. Your command line doesn't set any custom method but uses POST (implied by -d).

There's some confusion among the quotes at the end of your jsonObj string, it should probably be:

char* jsonObj = "{\"Mode\":\"Auto\",\"type\":\"Single\",\"IP\":\"9.9.9.9\",\"FirmwarePath\":\"\" }";

Upvotes: 3

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