As others have said, you do not need the -1 in this case. If the array is fixed size, I would use strncpy
instead. It was made for copying strings - sprintf
was made for doing difficult formatting. However, if the size of the array is unknown or you are trying to determine how much storage is necessary for a formatted string. This is what I really like about the Standard specified version of snprintf
:
char* get_error_message(char const *msg) {
size_t needed = snprintf(NULL, 0, "%s: %s (%d)", msg, strerror(errno), errno);
char *buffer = malloc(needed);
snprintf(buffer, needed, "%s: %s (%d)", msg, strerror(errno), errno);
return buffer;
}
Combine this feature with va_copy
and you can create very safe formatted string operations.