我如何读取未知长度的输入字符串？ [英] How can I read an input string of unknown length?

问题描述

如果我不知道这个词是怎么长的，我可以不写字符米[6]; ，结果
这个词的长度也许是十年，二长。
如何使用 scanf函数从键盘获取输入？

If I don't know how long the word is, I cannot write char m[6];,
The length of the word is maybe ten or twenty long. How can I use scanf to get input from the keyboard?

#include <stdio.h>
int main(void)
{
    char  m[6];
    printf("please input a string with length=5\n");
    scanf("%s",&m);
    printf("this is the string: %s\n", m);
    return 0;
}

请输入与lenght = 5结果字符串
你好结果
这是字符串：你好

please input a string with lenght=5
hello
this is the string: hello

推荐答案

输入，同时确保一个地区动态

例如

#include <stdio.h>
#include <stdlib.h>

char *inputString(FILE* fp, size_t size){
//The size is extended by the input with the value of the provisional
    char *str;
    int ch;
    size_t len = 0;
    str = realloc(NULL, sizeof(char)*size);//size is start size
    if(!str)return str;
    while(EOF!=(ch=fgetc(fp)) && ch != '\n'){
        str[len++]=ch;
        if(len==size){
            str = realloc(str, sizeof(char)*(size+=16));
            if(!str)return str;
        }
    }
    str[len++]='\0';

    return realloc(str, sizeof(char)*len);
}

int main(void){
    char *m;

    printf("input string : ");
    m = inputString(stdin, 10);
    printf("%s\n", m);

    free(m);
    return 0;
}

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