使用cJSON库更新json文件

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测试程序的目的是更新已有的json文件。

下面是测试程序的代码

#include "smartlight.h"#include "cJSON.h"cJSON *dofile(char *filename){FILE *f;long len;char *data;cJSON *json,*ret;f=fopen(filename,"rb");fseek(f,0,SEEK_END);len=ftell(f);fseek(f,0,SEEK_SET);data=(char*)malloc(len+1);fread(data,1,len,f);data[len]='\0';json=cJSON_Parse(data);if (!json) {printf("Error before: [%s]\n",cJSON_GetErrorPtr());ret = NULL;goto EXIT;}else{//printf("%s\n",data);ret = json;}EXIT:free(data);fclose(f);return ret;}int write_file(char *filename,char *out){FILE *fp = NULL;fp = fopen(filename,"a+");if(fp == NULL){fprintf(stderr,"open file failed\n");exit(-1);}fprintf(fp,"%s",out);if(fp != NULL)fclose(fp);}int main(){cJSON *root,*basicpara;char *out;root = dofile("basicparameter.cfg");out = cJSON_Print(root);printf("before modify:%s\n",out);free(out);basicpara = cJSON_GetObjectItem(root,"basicparameter");cJSON_GetObjectItem(basicpara,"mode")->valueint = 0;//cJSON_GetObjectItem(basicpara,"mode")->valuedouble = 0;cJSON_GetObjectItem(basicpara,"TimeoutPoweron")->valueint = 10;//cJSON_GetObjectItem(basicpara,"TimeoutPoweron")->valuedouble = 10;out = cJSON_Print(root);printf("after modify:%s\n",out);free(out);//write_file("basicparameter.cfg",out);cJSON_Delete(root);return 0;}

刚开始只修改了valueint的值，结果显示修改前后的结果一样。

cJSON_GetObjectItem(basicpara,"mode")->valueint = 0;

然后修改valuedouble的值，才能真能修改json文件。

如果只调用

cJSON_GetObjectItem(basicpara,"mode")->valuedouble = 0;

也只是修改了valuedouble的值。

所以如果想要修改valueint的值必须同时调用

cJSON_GetObjectItem(basicpara,"mode")->valueint = 0;cJSON_GetObjectItem(basicpara,"mode")->valuedouble = 0;

引用链接：https://sourceforge.net/p/cjson/discussion/998970/thread/5c13b93f/

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