使用scanf（）的动态分配 [英] Dynamic allocation with scanf()

问题描述

我的问题与此一个完全相同。也就是说，我试图使用 scanf（）接收一个不确定长度的字符串，我想要 scanf（）为它动态分配内存。

My question is exactly the same as this one. That is, I'm trying to use scanf() to receive a string of indeterminate length, and I want scanf() to dynamically allocate memory for it.

但是，在我的情况，我使用VS2010。据我所见，MS的 scanf（）没有或m修饰符用于扫描字符串。有没有办法做到这一点（除了一次接收一个字符输入）？

However, in my situation, I am using VS2010. As far as I can see, MS's scanf() doesn't have an a or m modifier for when scanning for strings. Is there any way to do this (other than receiving input one character at a time)?

推荐答案

如果你想使用 scanf 你可以分配一个足够大的缓冲区来保存任何可能的值，比如1024字节，然后使用1024的最大字段宽度说明符。

If you want to use scanf you could just allocate a large enough buffer to hold any possible value, say 1024 bytes, then use a maximum field width specifier of 1024.

m 和 a 是特定的非标准GNU扩展，因此Microsofts编译器不支持他们。

The m and a are specific non-standard GNU extensions, so thats why Microsofts compiler does not support them. One could wish that visual studio did.

下面是使用 scanf 读取设置的示例，退出：
#include
#include
#include

Here is an example using scanf to read settings, and just print them back out: #include #include #include

int
main( int argc, char **argv )
{   // usage ./a.out < settings.conf

    char *varname;
    int value, r, run = 1;

    varname = malloc( 1024 );

    // clear errno
    errno = 0;

    while( run )
    {   // match any number of "variable = #number" and do some "processing"

        // the 1024 here is the maximum field width specifier.
        r = scanf ( "%1024s = %d", varname, &value );
        if( r == 2 )
        {   // matched both string and number
            printf( " Variable %s is set to %d \n", varname, value );
        } else {
            // it did not, either there was an error in which case errno was
            // set or we are out of variables to match
            if( errno != 0 )
            {   // an error has ocurred.
                perror("scanf");
            }
            run = 0;
        }
    }

    return 0;
}

下面是一个示例 settings.conf

cake = 5
three = 3
answertolifeuniverseandeverything = 42
charcoal = -12

您可以阅读有关 scanf 。

You can read more about scanf on the manpages.

您当然可以使用 getline（） 。

如果你想多做一些你想达到的目标，你可能会得到一个更好的答案。

If you would go into a little more what you are trying to achieve you could maybe get an better answer.

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