Question

我使用Arduino和Open Weather Map API创建了一个气象站，但是我很难将响应解析成对sscanf有用的东西。

以下是一个回复示例：

{"coord":{"lon":-0.13,"lat":51.51},"weather":[{"id":800,"main":"Clear","description":"clear sky","icon":"01d"}],"base":"cmc stations","main":{"temp":14.17,"pressure":1012,"humidity":74,"temp_min":13,"temp_max":15.8},"wind":{"speed":4.6,"deg":150},"clouds":{"all":0},"dt":1459602835,"sys":{"type":1,"id":5091,"message":0.0059,"country":"GB","sunrise":1459575095,"sunset":1459622222},"id":2643743,"name":"London","cod":200}

我想从以下网址解析天气信息（清除）：

"weather":[{"id":800,"main":"Clear",

来自：

的临时信息（14）

"main":{"temp":14.17,

这是代码，我正在使用：

if (character == '}') { // Just a delimiter
      if (strstr(response, "\"weather\":[{")) { // to confirm that the string was found
        sscanf(response, ",main\":%s,", weather);
        Serial.printfn("\r\nfound weather = %s"), weather;
      }
      else if (strstr(response, "\"main\":{\"temp\":")) { // to confirm that the string was found
        sscanf(response, "temp\":%2s,", temp);
        Serial.printfn("\r\nfound temp = %s"), temp;
      }
      memset(response, 0, sizeof(response));
      idx = 0;
    }

但是sscanf甚至没有工作，因为它总是打印32个字节长的整个天气/临时字符串。

found weather = ,"weather":[{"id":800,"main":"Clear","description":
found temp = ],"base":"cmc stations","main":{"temp":14.17,"pressure":1011,"humi

任何人都有任何线索如何使用sscanf解析这些字符串？

Answer 1

这是example。把它翻译成你需要的任何C-Dialect。

#include <cstdio>
#include <cstring>
#include <iostream>

const char* haystack = "\"weather\":[{\"id\":800,\"main\":\"Clear\",";
const char* needle   = "\"main\":";

int main()
{
    std::cout << "Parsing string: '" << haystack << "'\n";

    if (const char* cursor = strstr(haystack, needle)) {
        char buffer[100];
        if (sscanf(cursor, "\"main\":\"%99[^\"]\",", buffer))
            std::cout << "Parsed string: '" << buffer << "'\n";
        else 
            std::cout << "Parsing error!\n";
    } else {
        std::cout << "Could not find '" << needle << "' in '" << haystack << "'\n";
    }
}

Answer 2

如果Serial.printfn是一个指向像printf（）那样工作的函数的指针，那么

Serial.printfn("\r\nfound weather = %s"), weather;

是未定义的行为，可能会打印您看到的内容。你应该使用

Serial.printfn("\r\nfound weather = %s", weather);

带双引号的sscanf

2 个答案: