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

All *printf functions check formatting and expand its corresponding argument, thus it is slower than a simple strcpy/strncpy, which only copy a given number of bytes from linear memory.

My rule of thumb is:

• Use snprintf whenever formatting is needed.
• Stick to strncpy/memcpy when only need to copy a block of linear memory.
• You can use strcpy whenever you know exatcly the size of buffers you're copying. Don't use that if you don't have full control over the buffers size.