de>#include<stdio.h>

#include<stdlib.h>

#define MAX_LEN 255

int my_strlen1(const char* str);

int my_strlen2(char* str);

int main()

{

    char str1[MAX_LEN];

    printf("Please input the string you want to strlen:\n");

    fgets(str1,256,stdin);

    printf("Length of %s is %d\n",str1,my_strlen1(str1));

    

    char* str2="Hello,world!";

    printf("Length of %s is %d\n",str2,my_strlen2(str2));

    exit(EXIT_SUCCESS);

}

/*strlen,定义变量的写法*/

int my_strlen1(const char* str)

{

    int len=0;

    while(*(str+len)!='\0')

        len++;

    return len;

}

/*strlen,不用变量,递归的写法*/

int my_strlen2(char* str)

{

    if(*str=='\0')

        return 0;

    else

        return (1+my_strlen2(++str));

}de>

de>/*zj@zj:~/C_parm/string/own_str$ gcc -o strlen strlen.c

 zj@zj:~/C_parm/string/own_str$ ./strlen

 Please input the string you want to strlen:

 hello,world!

 Length of hello,world!

 is 13

 Length of Hello,world! is 12

 *

 *聪明的你也许发现那里有点不对劲了,对一个是12,一个是13！

 其实strlen是不计算最后的字符串结束符'\0'的,那为什么有13呢?

  看输出就知道了,有个换行符号,对就是你输入时的结束符,回车了哦*/de>