仿写cp命令

在《unix环境高级编程》书中，有用read和write对标准输入和标准输出文件描述符进行操作以达到复制功能。受此启发，用open，write和read等函数仿写了一个cp命令。代码如下：

#include 
#include 
#include 
#include 
#include 
#include 

#define MAXBUF 4096

int main(int argc, char *argv[])
{
    int oldfiledes, newfiledes, n;
	off_t oldfilelength;
	char *pfilename = argv[1] + strlen(argv[1]) - 1;
	char *pdestpath = NULL;
	char *p1;
	char *buf = NULL;
	
	if (strlen(argv[1]) == 0 || strlen(argv[2]) == 0)
	{
		printf("Usage:my_copy filename destnation\n");
		exit(0);
	}
	
	if (strstr(argv[1], "/") != NULL)
	{
		while(1)
		{
			if (*--pfilename == '/')
			{
				*pfilename++;
				break;
			}
		}
	}
	else
	{
		pfilename = argv[1];
	}
	
	pdestpath = (char *)malloc(strlen(argv[2])+2);
	if (pdestpath == NULL)
		printf("malloc error\n");
	p1 = pdestpath;
	memset(pdestpath, 0, strlen(argv[2]) + 2);
	strcpy(pdestpath, argv[2]);
	
	if ((pdestpath = strstr(pdestpath, "/")) == NULL)
	{
		strcat(pdestpath,"/");
	}
	else if (*(--pdestpath) == '.')
	{
		pdestpath += 2;
		if (strstr(pdestpath, "/") == NULL)
		{
			memset(pdestpath, 0, strlen(argv[2]) + 1);
		}			strcpy(pdestpath, argv[2]);
			*(pdestpath + strlen(argv[2])) = '/';

	}

	strcat(pdestpath, pfilename);
	
	if (-1 == (oldfiledes = open(argv[1], O_RDONLY)))
	{
		printf("open oldfiledes error\n");
	}
	
	if (-1 == (newfiledes = open(pdestpath, O_WRONLY | O_CREAT | O_TRUNC, 0666)))
	{
		printf("open newfiledes error\n");
		exit(-1);
	}
	
	if (-1 == (oldfilelength = lseek(oldfiledes, 0, SEEK_END)))
	{
 		exit(-1);		exit(-1);

	}
	
	buf = (char *)malloc((long)(oldfilelength + 1));
	if (buf == NULL)
		printf("malloc error\n");
	printf("buf [%p]\n", buf);
	memset(buf, '0', oldfilelength + 1);
		
	if (-1 == lseek(oldfiledes, 0, SEEK_SET))
	{
		printf("lseek begin error\n");
		exit(-1);
	}

	if ((n = read(oldfiledes, buf, oldfilelength)) > 0)
	{
		printf("--buf [%p] n [%d] length =[%d]\n", buf, n, strlen(buf));
		printf("oldfilelength=[%ld]\n", oldfilelength);
		if (n != write(newfiledes, buf, n))
		{
			printf("write error \n");
			exit(-1);
		}
	}
	else 
	{
		printf("read error nResult[%d]\n", n);
		exit(-1);
	}
	
	printf("##buf [%p] n [%d] length =[%d]\n", buf, n, strlen(buf));
	printf("oldfilelength=[%ld]\n", oldfilelength);
	
	close(oldfiledes);
	close(newfiledes);
	pdestpath = p1;
	free(pdestpath);
	free(buf);
	
	return 0;
}

此代码能实现基本的复制功能，但是在本地运行时，提示free指针地址错误，用valgrind却没有看到内存泄露，并且在朋友的虚拟机中运行没有提示free报错。很迷茫，待以后深入了解之后再回来查看具体原因。