Linux C 编程——使用json-c库读取json格式的配置文件

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我是靠谱客的博主勤恳御姐，最近开发中收集的这篇文章主要介绍Linux C 编程——使用json-c库读取json格式的配置文件，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

1. 简介：
参考：

https://github.com/json-c/json-c/wiki

https://github.com/json-c/json-c

https://blog.csdn.net/u014530704/article/details/72674642?utm_source=copy

https://blog.csdn.net/w_ww_w/article/details/8295027

重点哈：https://blog.csdn.net/qimi123456/article/details/80426474

2. 编译运行：
json-c GitHub repo: https://github.com/json-c/json-c

$ git clone https://github.com/json-c/json-c.git
$ cd json-c
$ sh autogen.sh
followed by

$ ./configure # --enable-threading
$ make
$ make install
To build and run the test programs:

$ make check
$ make USE_VALGRIND=0 check # optionally skip using valgrind
3. 简单测试
1. 测试前，创建配置文件test.json，内容如下：

[root@localhost tests]# cat test.json
{"cmd":"SetPwd","params":{"id":111,"password":"test"}}
2. 编写测试文件test.c，内容如下：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include "../json.h"

void main()
{
/*从文件中获取json对象*/
struct json_object * json_policy_array;
json_policy_array = json_object_from_file("./test.json");
printf("%sn",json_object_to_json_string(json_policy_array));

/*从json对象中获取json对象*/
struct json_object * json_cmd ;
json_cmd = json_object_object_get(json_policy_array,"cmd");
printf("%sn",json_object_to_json_string(json_cmd));

/*从json对象中获取json对象*/
struct json_object * json_params ;
json_params = json_object_object_get(json_policy_array,"params");
printf("%sn",json_object_to_json_string(json_params));

int id = -1; //用于保存账号的值
int pwd_len = 0;
char *pwd = NULL; //用于保存密码的值
char *cmd = NULL; //用于保存cmd的值

/*从json对象中获取数据，首先获取对象，然后进行类型转换，转成int、float、string等*/
id = json_object_get_int(json_object_object_get(json_params,"id"));
printf("id = %dn", id);
cmd = json_object_get_string(json_object_object_get(json_policy_array,"cmd"));
printf("cmd = %sn", cmd);

pwd_len = json_object_get_string_len(json_object_object_get(json_params,"password"));
pwd = json_object_get_string(json_object_object_get(json_params,"password"));
printf("pwd_len = %dn", pwd_len);
printf("pwd = %sn", pwd);

/*向json文件中添加数据*/
//创建一个json对象newPobj
char *result = "OK";
//往json_policy_array里面添加键值对
json_object_object_add(json_policy_array,"result",json_object_new_string(result));

//创建一个json对象paramsProbj
json_object *paramsProbj = NULL;
paramsProbj = json_object_new_object();
//往paramsProbj里面添加键值对
json_object_object_add(paramsProbj,"id",json_object_new_int(200));
json_object_object_add(paramsProbj,"password",json_object_new_string("password2"));
//把paramsProbj添加到newPobj对象中
json_object_object_add(json_params,"paramsProbj",paramsProbj);

//这时还是将配置信息存在内存中呢
printf("%sn",json_object_to_json_string(json_policy_array));

//将内存中修改后的配置文件，写会到磁盘中
json_object_to_file("./test.json",json_policy_array);

//释放内存
//引用计数方式，无需手动释放
}
3. 编译

[root@localhost tests]# gcc -ljson-c test.c
test.c: In function ‘main’:
test.c:32:6: warning: assignment discards ‘const’ qualifier from pointer target type [enabled by default]
cmd = json_object_get_string(json_object_object_get(json_policy_array,"cmd"));
^
test.c:36:6: warning: assignment discards ‘const’ qualifier from pointer target type [enabled by default]
pwd = json_object_get_string(json_object_object_get(json_params,"password"));
^
4.运行

[root@localhost tests]# ./a.out
{ "cmd": "SetPwd", "params": { "id": 111, "password": "test" } }
"SetPwd"
{ "id": 111, "password": "test" }
id = 111
cmd = SetPwd
pwd_len = 4
pwd = test
{ "cmd": "SetPwd", "params": { "id": 111, "password": "test", "paramsProbj": { "id": 200, "password": "password2" } }, "result": "OK" }
运行后，配置文件内容如下：

[root@localhost tests]# cat test.json
{"cmd":"SetPwd","params":{"id":111,"password":"test","paramsProbj":{"id":200,"password":"password2"}},"result":"OK"}
4. 项目应用
在项目中，可以对此开源库进行封装，以使用项目本身；

为了是运行中的进程能够在配置文件改变后重新读取，需要引入信号机制：

1. 可以直接在信号处理函数中重新读取配置文件；

2. 也可以使用单独的线程，线程阻塞等待信号量，信号处理函数中释放信号量，线程获得信号量后，读写配置文件。
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版权声明：本文为CSDN博主「江山美人1」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/u011285208/article/details/90293384