c strcat

cat strcat.c
/*
 * Concatenates src onto the end of dest.
 * Assumes enough space in dest.
 * 目标指针空间必须有足够的存储空间。
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define MAX_LEN 255
char* my_strcat1(char* dst,const char* src);
char* my_strcat2(char* dst,const char* src);

int main()
{
   char str1[MAX_LEN] = "zj,";
   char* str2 = "ubuntuer!";
   char* str3 = "centoser!";
   printf("After strcat1:%s\n",my_strcat1(str1,str2));
   printf("After strcat2:%s\n",my_strcat2(str1,str3));
   exit(EXIT_SUCCESS);
}

char* my_strcat1(char* dst, const char* src )
{
    char* p = dst;
    while(*p)p++;
    while((*p++ =*src++)!='\0')
    ;
    return( dst );
}
/*这个貌似就有点没意思了哦,不过你还是不介意可以把自己写的
 * strlen和strcpy copy过来呵呵^_^
 * 自己去diy把*/
char* my_strcat2(char* dst,const char* src)
{
    char* p = dst;
    p += strlen(dst);
    strcpy(p,src);
    return dst;
}

zj@zj:~/C_parm/string/own_str/strcat$ ./strcat
After strcat1:zj,ubuntuer!
After strcat2:zj,ubuntuer!centoser!




cat strncat.c
/*
 * Concatenates src onto the end of dest.
 * Assumes enough space in dest.
 * 目标指针空间必须有足够的存储空间。
 * The strncat() function is similar, except that it will use
 *at most n characters from src; and src does not need to be
 *null terminated if it contains n or more characters.
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define MAX_LEN 255
char* my_strncat1(char* dst,const char* src,int n);
char* my_strncat2(char* dst,const char* src,int n);

int main()
{
   char str1[MAX_LEN] = "zj,";
   char* str2 = "ubuntuer!";
   char* str3 = "debianer!";

   printf("After strncat1:%s\n",my_strncat1(str1,str2,6));
   printf("After strncat2:%s\n",my_strncat2(str1,str3,9));

   exit(EXIT_SUCCESS);
}

char* my_strncat1(char* dst,const char* src,int n)
{
    char* p = dst;
    while(*p)
    p++;
    while((n--)&&(*src++!='\0'))
        *p++=*src;
    *p='\0';
    return(dst);
}

/*这个貌似就有点没意思了哦,不过你还是不介意可以把自己写的
 * strlen和strcpy copy过来呵呵^_^
 * 自己去diy把*/
char* my_strncat2(char* dst,const char* src,int n)
{
    char* p = dst;
    p += strlen(dst);
    strncpy(p,src,n);
     *(p+strlen(dst))='\0';
    return dst;
}

zj@zj:~/C_parm/string/own_str/strncat$ ./strncat
After strncat1:zj,buntue
After strncat2:zj,buntuedebianer!