C fscanf 奇怪地连接两个字符串

发布于 2024-11-09 05:51:30 字数 438 浏览 0 评论 0原文

这个程序真的让我很紧张：

我试图从文件中读取一行，其中包含以下信息：

512 MB 136.186.99.1 00-25-B3-0B-31-29

其格式为双字符串字符串

，我正在使用的代码是

fscanf(filePtr, "%lf %s %s %s", &Computer[i].ram, Computer[i].ram_unit, Computer[i].MACNo, Computer[i].IPV4);

但是当我打印 Computer[i].ram_unit 我得到：

MB136.186.99.1

请帮助我找出我做错了什么。如果您希望我粘贴整个代码，请告诉我。

谢谢

原文

This program is really getting on my nerves:

I am trying to read a line from a file with following information:

512 MB 136.186.99.1 00-25-B3-0B-31-29

which is in the format of double string string string

and the code I'm using is

fscanf(filePtr, "%lf %s %s %s", &Computer[i].ram, Computer[i].ram_unit, Computer[i].MACNo, Computer[i].IPV4);

but when I print Computer[i].ram_unit I get:

MB136.186.99.1

Please help me to find out what I'm doing wrong. Let me know if you like me to paste the entire code.

Thanks

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绝影如岚 2024-11-16 05:51:30

首先，您在 fscanf 中相对于示例输入颠倒了 MACNo 和 IPV4。

在没有看到结构定义的情况下无法确定，但看起来可能是数组溢出。例如，如果您的Computer定义如下：

struct ComputerType {
    double ram;
    char ram_unit[2];  /* This needs to be 3 (assuming unit is always 2 chars long) */
    char IPV4[16];
    char MACNo[17];
};

当您将“MB”读入ram_unit时，您最终可能会得到

ram_unit[0] = 'M'
ram_unit[1] = 'B'
IPV4[0] = '\0'

然后当您将IP地址读入IPV4时这使得

ram_unit[0] = 'M'
ram_unit[1] = 'B'
IPV4[0] = '1'
IPV4[1] = '3'
[etc]
IPV4[10] = '1'
IPV4[11] = '\0'

当你去打印 ram_unit 时，打印函数将从内存位置 &ram_unit[0] 开始并继续打印，直到看到 >空。但由于 NULL 最终出现在 IPV4[0] 中，并且当您读取 IP 地址时它被覆盖，因此它不会停止打印，直到到达 NULL IPV4[11] 所以你会得到意想不到的串联。

First, you have MACNo and IPV4 reversed in your fscanf relative to the sample input.

Can't tell for sure without seeing the structure definition, but it looks like a possible array overrun. For example, if your Computer was defined like this:

struct ComputerType {
    double ram;
    char ram_unit[2];  /* This needs to be 3 (assuming unit is always 2 chars long) */
    char IPV4[16];
    char MACNo[17];
};

when you read "MB" into ram_unit, you could end up having

ram_unit[0] = 'M'
ram_unit[1] = 'B'
IPV4[0] = '\0'

And then when you read in the IP address into IPV4 that makes it

ram_unit[0] = 'M'
ram_unit[1] = 'B'
IPV4[0] = '1'
IPV4[1] = '3'
[etc]
IPV4[10] = '1'
IPV4[11] = '\0'

When you go to print out ram_unit, the print function will start at the memory location &ram_unit[0] and keep on printing until it sees a NULL. But since the NULL ended up in IPV4[0] and that got overwritten when you read in the IP address, it won't stop printing until it gets to the NULL at IPV4[11] and so you get the unexpected concatenation.

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掌心的温暖 2024-11-16 05:51:30

要从这样的文件中读取一行：

1603 Lu,Ma,Mi,Ju,Vi,Sa,No Mar del Plata 08:25 09:20 阿根廷航空公司

使用此：

fscanf(pf, "%d %2s,%2s,%2s,%2s,%2s,%2s,%2s %[^\n]s %d:%d %d:%d %[^\n]s",
    ®istro.code,
    ®istro.dia.lunes,
    ®istro.dia.martes,
    ®istro.dia.miercoles,
    ®istro.dia.jueves,
    ®istro.dia.viernes,
    ®istro.dia.sabado,
    ®istro.dia.domingo,
    ®istro.destino,
    ®istro.hSalida.hh,
    ®istro.hSalida.mm,
    ®istro.hLlegada.hh,
    ®istro.hLlegada.mm,
    ®istro.aerolinea
);

To read a line from a file like this one:

1603 Lu,Ma,Mi,Ju,Vi,Sa,No Mar del Plata 08:25 09:20 Aerolineas Argentinas

Use this:

fscanf(pf, "%d %2s,%2s,%2s,%2s,%2s,%2s,%2s %[^\n]s %d:%d %d:%d %[^\n]s",
    ®istro.code,
    ®istro.dia.lunes,
    ®istro.dia.martes,
    ®istro.dia.miercoles,
    ®istro.dia.jueves,
    ®istro.dia.viernes,
    ®istro.dia.sabado,
    ®istro.dia.domingo,
    ®istro.destino,
    ®istro.hSalida.hh,
    ®istro.hSalida.mm,
    ®istro.hLlegada.hh,
    ®istro.hLlegada.mm,
    ®istro.aerolinea
);

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