snprintf vs. strcpy (etc.) in C

Question

For doing string concatenation, I\'ve been doing basic strcpy, strncpy of char* buffers. Then I learned about the snprintf and friends

Answer 1

As others did point out already: Do not use strncpy.

• strncpy will not zero terminate in case of truncation.
• strncpy will zero-pad the whole buffer if string is shorter than buffer. If buffer is large, this may be a performance drain.

snprintf will (on POSIX platforms) zero-terminate. On Windows, there is only _snprintf, which will not zero-terminate, so take that into account.

Note: when using snprintf, use this form:

snprintf(buffer, sizeof(buffer), "%s", string);

instead of

snprintf(buffer, sizeof(buffer), string);

The latter is insecure and - if string depends on user input - can lead to stack smashes, etc.