http://www.hmug.org/man/3/printf.php
o An optional length modifier, that specifies the size of the
argument.
The following length modifiers are valid for the d, i, n, o, u, x,
or
X conversion:
Modifier d, i o, u, x, X n
hh signed char unsigned char signed char *
h short unsigned short short *
l (ell) long unsigned long long *
ll (ell ell) long long unsigned long long long long *
j intmax_t uintmax_t intmax_t *
t ptrdiff_t (see note) ptrdiff_t *
z (see note) size_t (see note)
q (deprecated) quad_t u_quad_t quad_t *
Note: the t modifier, when applied to a o, u, x, or X conversion,
indicates that the argument is of an unsigned type equivalent in
size
to a ptrdiff_t. The z modifier, when applied to a d or i
conversion,
indicates that the argument is of a signed type equivalent in size
to
a size_t. Similarly, when applied to an n conversion, it indicates
that the argument is a pointer to a signed type equivalent in size
to
a size_t.
The following length modifier is valid for the a, A, e, E, f, F, g,
or G conversion:
Modifier a, A, e, E, f, F, g, G
l (ell) double (ignored, same behavior as without it)
L long double
The following length modifier is valid for the c or s conversion:
Modifier c s
l (ell) wint_t wchar_t *
The AltiVec Technology Programming Interface Manual also defines
five
additional length modifiers which can be used (in place of the con-
ventional length modifiers) for the printing of AltiVec vectors:
v Treat the argument as a vector value, unit length will
be
determined by the conversion specifier (default = 16
8-bit units for all integer conversions, 4 32-bit units
for floating point conversions).
vh, hv Treat the argument as a vector of 8 16-bit units.
vl, lv Treat the argument as a vector of 4 32-bit units.
NOTE: The vector length specifiers are AltiVec only extensions onto
the printf() specification. Behaviour of these values for printf()
is only defined for operating systems conforming to the AltiVec
Tech-
nology Programming Interface Manual. (At time of writing this
includes only Mac OS X 10.2 and later.)