The short answer is that it has no impact on printf, and denotes use of float or double in scanf. For printf, arguments of type float are promoted to double so both %f and %lf are used for double. For scanf, you should use %f for float and %lf for double. More detail for the … Read more
Checking if 2 printf() format strings are compatible is an exercise in format parsing. C, at least, has no standard run-time compare function such as: int format_cmp(const char *f1, const char *f2); // Does not exist Formats like “%d %f” and “%i %e” are obviously compatible in that both expect an int and float/double. Note: … Read more
You can escape the % character: [DisplayFormat(DataFormatString = @”{0:#\%}”)] Note that there are two ways to use \ as an escape character: if you prefix a string literal with the verbatim symbol (@), then \ characters are included in the string as-is, which means that as part of a format string a single \ will … Read more
You may be able to exploit a format string vulnerability in many ways, directly or indirectly. Let’s use the following as an example (assuming no relevant OS protections, which is very rare anyways): int main(int argc, char **argv) { char text[1024]; static int some_value = -72; strcpy(text, argv[1]); /* ignore the buffer overflow here */ … Read more
Yes: use the z length modifier: size_t size = sizeof(char); printf(“the size is %zu\n”, size); // decimal size_t (“u” for unsigned) printf(“the size is %zx\n”, size); // hex size_t The other length modifiers that are available are hh (for char), h (for short), l (for long), ll (for long long), j (for intmax_t), t (for … Read more
Most of these answers explain what %n does (which is to print nothing and to write the number of characters printed thus far to an int variable), but so far no one has really given an example of what use it has. Here is one: int n; printf(“%s: %nFoo\n”, “hello”, &n); printf(“%*sBar\n”, n, “”); will … Read more
You can escape it by posting a double ‘%’ like this: %% Using your example: printf(“hello%%”); Escaping the ‘%’ sign is only for printf. If you do: char a[5]; strcpy(a, “%%”); printf(“This is a’s value: %s\n”, a); It will print: This is a’s value: %%