Format it yourself (see Format Specification Mini-Language): for ix in [.02e9, .2e9, 2e9, 20e9, 200e9, 2000e9]: print(‘{:.3e} => {:0=8.3f}e9’.format(ix, ix / 1e9)) Output 2.000e+07 => 0000.020e9 2.000e+08 => 0000.200e9 2.000e+09 => 0002.000e9 2.000e+10 => 0020.000e9 2.000e+11 => 0200.000e9 2.000e+12 => 2000.000e9 Explanation {:0=8.3f} means “zero-pad, pad between the sign and the number, total field width … Read more
I don’t know what POSIX has to say about this, but this is nicely handled by core C99: #include <stdio.h> #include <inttypes.h> int main(void) { uint64_t dbFileSize = 99; uint64_t fileSize = 100; char buf[128]; memset(buf, 0x00, 128); sprintf( buf, “\nOD DB File Size = %” PRIu64 ” bytes \t” ” XML file size = … Read more
This is the full description of the g/G specifier in the C11 standard: A double argument representing a floating-point number is converted in style f or e (or in style F or E in the case of a G conversion specifier), depending on the value converted and the precision. Let P equal the precision if … Read more
There is none. Use a temp object as the size of _Bool is implementation dependent. #include <stdbool.h> #include <stdio.h> bool b; int temp; scanf(“%d”, &temp); b = temp;
From the latest C11 draft — §7.16 Variable arguments <stdarg.h>: §7.16.1.1/2 …if type is not compatible with the type of the actual next argument (as promoted according to the default argument promotions), the behavior is undefined, except for the following cases: — one type is a signed integer type, the other type is the corresponding … Read more
It is consistent behavior, you’re just thinking about it wrong. 😉 scanf(“%c”, some_char); // reads a character from the key board. scanf(“%d”, some_int); // reads an integer from the key board. So if I do this: printf(“Insert a character: “); scanf(“%c”, &ch); // if I enter ‘f’. Really I entered ‘f’ + ‘\n’ // scanf … Read more
If you read the specification for scanf() carefully, most format specifiers skip leading white space. In Standard C, there are three that do not: %n — how many characters have been processed up to this point %[…] — scan sets %c — read a character. (POSIX adds a fourth, %C, which is equivalent to %lc.) … Read more
MS Visual Studio didn’t support %zu printf specifier before VS2013. Starting from VS2013 (e.g. _MSC_VER >= 1800) %zu is available. As an alternative, for previous versions of Visual Studio if you are printing small values (like number of elements from std containers) you can simply cast to an int and use %d: printf(“count: %d\n”, (int)str.size()); … Read more
Breakdown of scanf(“%*[^\n]%*c”): %*[^\n] scans everything until a \n, but doesn’t scan in the \n. The asterisk(*) tells it to discard whatever was scanned. %*c scans a single character, which will be the \n left over by %*[^\n] in this case. The asterisk instructs scanf to discard the scanned character. Both %[ and %c are … Read more
printf(“Hello World!”); is IMHO not vulnerable but consider this: const char *str; … printf(str); If str happens to point to a string containing %s format specifiers, your program will exhibit undefined behaviour (mostly a crash), whereas puts(str) will just display the string as is. Example: printf(“%s”); //undefined behaviour (mostly crash) puts(“%s”); // displays “%s\n”