On Thu, Aug 5, 2010 at 9:18 PM, Changli Gao <xiaosuo@xxxxxxxxx> wrote: > On Thu, Aug 5, 2010 at 7:37 PM, Dan Carpenter <error27@xxxxxxxxx> wrote: >> >> Both strncpy() and strlcpy() take a limitter. The difference is that >> strlcpy() always takes on a terminator and strncpy() only adds a >> terminator if there is space. >> >> strlcpy() is a BSD function that never caught on in Linux. The glibc >> maintainers think that if you accidentally chop off the last part of a >> word that makes you an idiot. They think you should known the length of >> your data at all times and use memcpy() or a proper string library. >> >> I prefer strlcpy() to strncpy(). Some people do stuff like: >> strncpy(bar, foo, n); >> bar[n] = '\0'; >> You have to read through the code to find if n is "sizeof(bar)" or >> "sizeof(bar) - 1". Which is a pain in the arse. strlcpy() is explicit >> and it's just one line of code instead of two. >> >> The other tricky thing you should remember about strncpy() is that the >> posix version writes NUL chars from the end of the string to the >> limitter but the kernel version only copies one NUL character. >> > > You should spend some time on reading the source code of strlcpy() and > strncpy(). > > the example use of them is: > > char dst[24]; > char *src = "test"; > > strncpy(dst, src, sizeof(dst) - 1); Oh, Sorry, I made a mistake here. As you said, the code should be strncpy(dst, src, sizeof(dst)); dst[sizeof(dst) - 1] = '\0'; However, if you use strlcpy(), you really don't need to zero the dst buffer. > strlcpy(dst, src, sizeof(dst)); > > both of them don't need to zero dst, and they don't need to pad zero > at then end of the dst. > -- Regards, Changli Gao(xiaosuo@xxxxxxxxx) -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
