使用c++读取json文件的代码

以下是使用c语言读取json文件的示例代码：

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

int main() {
    char *filename = "data.json";
    char *data = NULL;
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        printf("Failed to open %s\n", filename);
        return 1;
    }
    fseek(fp, 0, SEEK_END);
    long length = ftell(fp);
    fseek(fp, 0, SEEK_SET);
    data = (char *) malloc(length + 1);
    fread(data, 1, length, fp);
    fclose(fp);
    data[length] = '\0';
    cJSON *json = cJSON_Parse(data);
    if (json == NULL) {
        const char *error_ptr = cJSON_GetErrorPtr();
        if (error_ptr != NULL) {
            printf("Error before: %s\n", error_ptr);
        }
        return 1;
    }
    cJSON *name = cJSON_GetObjectItemCaseSensitive(json, "name");
    if (cJSON_IsString(name) && (name->valuestring != NULL)) {
        printf("Name: %s\n", name->valuestring);
    }
    cJSON *age = cJSON_GetObjectItemCaseSensitive(json, "age");
    if (cJSON_IsNumber(age)) {
        printf("Age: %d\n", age->valueint);
    }
    cJSON *address = cJSON_GetObjectItemCaseSensitive(json, "address");
    cJSON *city = cJSON_GetObjectItemCaseSensitive(address, "city");
    if (cJSON_IsString(city) && (city->valuestring != NULL)) {
        printf("City: %s\n", city->valuestring);
    }
    cJSON_Delete(json);
    free(data);
    return 0;
}

此代码使用了cJSON库，需要先安装该库。在Ubuntu下，可以使用以下命令安装：

sudo apt-get install libjansson-dev