Question

如何在不指定大小的情况下将无限字符读入char*变量？

例如，假设我想要读取也可能需要多行的员工的地址。

Answer 1

你必须首先“猜测”你期望的大小，然后使用malloc分配一个大的缓冲区。如果结果太小，则使用realloc来调整缓冲区的大小。示例代码：

char *buffer;
size_t num_read;
size_t buffer_size;

buffer_size = 100;
buffer = malloc(buffer_size);
num_read = 0;

while (!finished_reading()) {
    char c = getchar();
    if (num_read >= buffer_size) {
        char *new_buffer;

        buffer_size *= 2; // try a buffer that's twice as big as before
        new_buffer = realloc(buffer, buffer_size);
        if (new_buffer == NULL) {
            free(buffer);
            /* Abort - out of memory */
        }

        buffer = new_buffer;
    }
    buffer[num_read] = c;
    num_read++;
}

这只是我的头脑，可能（读：可能会）包含错误，但应该给你一个好主意。

Answer 2

刚刚不得不回答Ivor Horton第3版的Ex7.1，第130页的Beginning C。花了几周时间锻炼身体。允许输入浮动数字而不预先指定用户将输入多少个数字。将数字存储在动态数组中，然后打印出数字和平均值。在Ubuntu 11.04中使用Code :: Blocks。希望它有所帮助。

/*realloc_for_averaging_value_of_floats_fri14Sept2012_16:30  */

#include <stdio.h>
#include <stdlib.h>
#define TRUE 1

int main(int argc, char ** argv[])
{
    float input = 0;
    int count=0, n = 0;
    float *numbers = NULL;
    float *more_numbers;
    float sum = 0.0;

    while (TRUE)
    {
        do
        {
            printf("Enter an floating point value (0 to end): ");
            scanf("%f", &input);
            count++;
            more_numbers = (float*) realloc(numbers, count * sizeof(float));
            if ( more_numbers != NULL )
            {
                numbers = more_numbers;
                numbers[count - 1] = input;
            }
            else
            {
                free(numbers);
                puts("Error (re)allocating memory");
                exit(TRUE);
            }
        } while ( input != 0 );

        printf("Numbers entered: ");
        while( n < count )
        {
            printf("%f ", numbers[n]);  /* n is always less than count.*/
            n++;
        }
        /*need n++ otherwise loops forever*/
        n = 0;
        while( n < count )
        {
            sum += numbers[n];      /*Add numbers together*/
            n++;
        }
        /* Divide sum / count = average.*/
        printf("\n Average of floats = %f \n", sum / (count - 1));
    }
    return 0;
}

/* Success Fri Sept 14 13:29 . That was hard work.*/
/* Always looks simple when working.*/
/* Next step is to use a function to work out the average.*/
/*Anonymous on July 04, 2012*/
/* http://www.careercup.com/question?id=14193663 */

Answer 3

如何在堆栈上放置一个1KB缓冲区（或4KB），直到找到地址的末尾，然后分配一个正确大小的缓冲区并将数据复制到它？从函数返回后，堆栈缓冲区消失，您只能调用malloc。

如何在C中读取无限字符

3 个答案: