strncat函数实现及简单应用 -

标题: strncat函数实现及简单应用 [打印本页]

作者: xiaojuan 时间: 2014-9-24 22:33
标题: strncat函数实现及简单应用

//:Vc++6.0  String  strncat函数
//功能：按照num数量连接num个字符
//参数：dest 目标字符串  str 连接字符串  num 连接个数
//返回值：目标字符串
#include<stdio.h>

char *strncat(char *dest, const char *str, int num);

int main()
{
char str1[20] = "hello ";
char str2[20] = "world haha";
char str3[20] = "heihei";
strncat(str3, strncat(str1, str2, 6), 5);
printf("str1 = %s\n", str3);
return 0;
}

char *strncat(char *dest, const char *str, int num)
{
if (dest == NULL || str == NULL)
{
perror("dest or str");
return NULL;
}
char *temp = dest;
const char *temp1 = str; //前面必须是const修饰的，否则编译不通过
int len;
while (*(temp1++) != '\0');
len = temp1 - str;
temp1 = str;

while (*(temp++) != '\0');
temp--;

if (num <= 0) //当num值小于0时，不连接
      *temp = '\0';
else if (num >= len) //当num值大于字符长度时，全部连接
{
      while (*(temp1) != '\0')
      {
         *(temp++) = *(temp1++);
      }
      *temp = '\0';
}
else
{
      for (int i = 0; i < num; i++)
      {
         *(temp++) = *(temp1++);
      }
      *temp = '\0';
}
return dest;
}

//在vc++6.0中的运行结果为：str1 = heiheihello//:~

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