strdup的原理以及用法

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

char* strDUP(char* str)
{
int len = strlen(str);
if(len <=0 )
return NULL;

char* p = (char*)malloc(len+1);
memset( p, 0, len+1);
memcpy( p, str, len);

return p;
}

int main(int argc, char* argv[])
{
char* str = "this is a demo for strdup()";

char* p = strDUP(str);

printf(p);
printf("\n");

free(p);

return 0;
}