strlcpy

strlcpy函数返回的是源字符串的长度  strlcat函数返回的是源字符串+目的字符串的长度   程序可通过返回的值
和目的字符串的SIZE比较  就可以知道在拷贝、粘帖过程中是否发生了截断 
strlcpy函数源码如下

#include

20

#include

21

22

/**

23	* Copy src to string dst of size siz.  At most siz-1 characters

24	* will be copied.  Always NUL terminates (unless siz == 0).

25	* Returns strlen(src); if retval >= siz, truncation occurred.

26

*/

27

size_t

28	strlcpy(char *dst, const char *src, size_t siz)

29

{

30	char *d = dst;

31	const char *s = src;

32	size_t n = siz;

33

34	/** Copy as many bytes as will fit */

35	if (n != 0) {

36	while (--n != 0) {

37	if ((*d++ = *s++) == '\0')

38

break;

39

}

40

}

41

42	/** Not enough room in dst, add NUL and traverse             rest of src */

43	if (n == 0) {

44	if (siz != 0)

45	*d = '\0'; /** NUL-terminate dst */

46	while (*s++)

47

;

48

}

49

50	return(s - src - 1);        /** count does not include NUL */

51

}

用法示例：

len = strlcpy(path, homedir,sizeof(path);
if (len >= sizeof(path))
return (ENAMETOOLONG);
len = strlcat(path, "/",sizeof(path);
if (len >= sizeof(path))
return (ENAMETOOLONG);
len = strlcat(path, ".foorc",sizeof(path));
if (len >= sizeof(path))
return (ENAMETOOLONG);