常见的C字符串处理函数的源代码

#include <stdio.h>

#include <assert.h>

char *strcpy(char *strDest,const char *strSrc) //复制字符串

{

assert((strDest!=NULL)&&(strSrc!=NULL));

char *address = strDest;

while((*strDest++=*strSrc++)!='\0')

NULL; //空语句

return address;

}

int strcmp(const char *s1,const char * s2)  //比较字符串

{

assert(s1!=NULL&&s2!=NULL);

while(*s1&&*s2&&*s1==*s2)

{

s1++;

s2++;

}

return (*s1-*s2);

}

char *strcat(char *strDes, const char *strSrc)//连接字符串

{

assert((strDes!=NULL)&&(strSrc!=NULL));

char *address = strDes;

while(*strDes!='\0')  //将原字符串指针移到最后一个字符

strDes++;

while((*strDes++=*strSrc++)!='\0')

NULL;

return address;

}

int strlen(const char *str) //求字符串长度

{

assert(str!=NULL);

int len = 0;

while(*str++!='\0')

{

len++;

}

return len;

}

int main(int argc, char* argv[])

{

char a[10];

strcpy(a,"hello world");

printf("%s\n",a);

char s1[]="abcd";

char s2[]="abcd";

int res = strcmp(s1,s2);

printf("%d\n",res);

char b[]="hello";

char c[]="world";

char d[20];

strcpy(d,b);

strcat(d,c);

printf("%s\n",d);

int len = strlen(a);

printf("%d\n",len);

return 0;

}