Use of C language cjson Library

Download first cJSON The library of , It's still easy to find a way to download

Unpacking a compressed package , The inside cJSON.h and cJSON.c Put it into your project , You can start playing

Let's start with a simple code ：

#include<stdio.h>
#include<stdlib.h>
#include"cJSON.h"

int main(void)
{
    char *data = "{\"jjj\":[\"kkk\",\"lll\"]}";
    // Parse from buffer JSON structure 
    cJSON * json= cJSON_Parse(data);

    // Will the incoming JSON Structure into a string   And print 
    char *json_data = NULL;
    printf("data:%s\n",json_data = cJSON_Print(json));

    free(json_data);
    // take JSON The data space occupied by the structure is released 
    cJSON_Delete(json);
    return 0;
}

Output results ：

data:{
	"jjj":	["kkk", "lll"]
}

---

Then you can advance , The code is as follows ：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include"cJSON.h"

int main(void)
{
    // Create an empty document （ object ）
    cJSON *json = cJSON_CreateObject();

    cJSON_AddItemToObject(json,"name",cJSON_CreateString(" Ma Baoguo "));
    // Add a key value pair to the document 
    //cJSON_AddItemToObject(json,"age",cJSON_CreateNumber(29));
    cJSON_AddNumberToObject(json," Age ",69);

    cJSON *array = NULL;
    cJSON_AddItemToObject(json," Skill ",array=cJSON_CreateArray());
    cJSON_AddItemToArray(array,cJSON_CreateString(" Mouse tail juice "));
    cJSON_AddItemToArray(array,cJSON_CreateString(" Lightning whip "));
    cJSON_AddItemToArray(array,cJSON_CreateString(" Don't talk about martial arts "));
    cJSON_AddNumberToObject(json,"score",0);
    cJSON_AddStringToObject(json,"address","xxx");

    // take json Structure format to buffer 
    char *buf = cJSON_Print(json);
    // Open file write json Content 
    FILE *fp = fopen("create.json","w");
    fwrite(buf,strlen(buf),1,fp);
    free(buf);
    fclose(fp);
    // Release json Memory occupied by structure 
    cJSON_Delete(json);
    return 0;
}

Output results （ Write to file ）：

{
	"name":	" Ma Baoguo ",
	" Age ":	69,
	" Skill ":	[" Mouse tail juice ", " Lightning whip ", " Don't talk about martial arts "],
	"score":	0,
	"address":	"xxx"
}

---

Then advance again ：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include"cJSON.h"

int main(void)
{
    // First create an empty object 
    cJSON *json = cJSON_CreateObject();
    // Add a key value pair to the object 
    cJSON_AddStringToObject(json,"country","china");
    // Add an array 
    cJSON *array = NULL;
    cJSON_AddItemToObject(json,"stars",array=cJSON_CreateArray());
    // Add object to array 
    cJSON *obj = NULL;
    cJSON_AddItemToArray(array,obj=cJSON_CreateObject());
    cJSON_AddItemToObject(obj,"name",cJSON_CreateString("Faye"));
    cJSON_AddStringToObject(obj,"address","beijing");
    // Add a key value pair to the object 
    cJSON_AddItemToArray(array,obj=cJSON_CreateObject());
    cJSON_AddItemToObject(obj,"name",cJSON_CreateString("andy"));
    cJSON_AddItemToObject(obj,"address",cJSON_CreateString("HK"));

    cJSON_AddItemToArray(array,obj=cJSON_CreateObject());
    cJSON_AddStringToObject(obj,"name","eddie");
    cJSON_AddStringToObject(obj,"address","TaiWan");

    // Cleaning work 
    FILE *fp = fopen("create.json","w");
    char *buf = cJSON_Print(json);
    fwrite(buf,strlen(buf),1,fp);
    fclose(fp);
    cJSON_Delete(json);
    return 0;
}

Output results （ Write it in a file ）：

{
	"country":	"china",
	"stars":	[{
			"name":	"Faye",
			"address":	"beijing"
		}, {
			"name":	"andy",
			"address":	"HK"
		}, {
			"name":	"eddie",
			"address":	"TaiWan"
		}]
}

---

compile ：

gcc json_example.c cJSON.c -o json_example -L . -lm

I believe after reading these examples , Write something a little more complicated json It's also completely OK. This thing is not difficult , Just be careful .