3.3.3 64-Bit Formatted Input/Output

64-bit values can be input and output using format strings that use 'L' as the prefix to one of the following conversion specifiers: d, i, o, u, x and X. For example:

printf("A big number: %Lx", ((longlong) 1) << 53);

will produce as output

A big number: 0020000000000000

Note that this usage of L is an extension to the ANSI C standard. It provides a useful interpretation for combinations of conversion specifiers that are otherwise undefined. It follows that use of L in this way may not be portable to other environments. (The standard defined usage of L as a prefix to e, E, f, g and G is not affected.)

The C libraries also support the conversion functions strtoq and strtouq.