sscanf 带双引号答案

【问题标题】：sscanf with double quotessscanf 带双引号
【发布时间】：2016-04-02 13:26:51
【问题描述】：

我正在使用 Arduino 和 Open Weather Map API 创建一个气象站，但我在将响应解析为 sscanf 有用的东西时遇到了严重的麻烦。

这是一个响应示例：

{"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}

我想从以下位置解析天气信息（清除）：

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

而临时信息 (14) 来自：

"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 sscanf 甚至无法正常工作，因为它总是打印 32 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

有人知道如何使用 sscanf 解析这些字符串吗？

【问题讨论】：

使用%[^\"] 表示“直到我读到\"”
您有sscanf_s 可用吗？或者 Arduinos 是否存在 Boost.Spirit？
is 'Serial.printfn("\r\nfound weather = %s"), weather;'正确的？不应该是 'Serial.printfn("\r\nfound weather = %s", weather);' ?
这是Demo。与@user3121023 所写的内容一起使用。
@12431234123412341234123 确实如此。这就是问题所在……该死，谢谢！！

标签： c arduino scanf double-quotes openweathermap

【解决方案1】：

这是example。将其翻译成您需要的任何 C 方言。

#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";
    }
}

【讨论】：

+ 用于变量名的不错选择；）

【解决方案2】：

如果 Serial.printfn 是一个指向类似 printf() 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);

【讨论】：