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The way printf
and sprintf
(see section Using printf
Statements for Fancier Printing)
perform rounding often depends upon the system's C sprintf
subroutine. On many machines, sprintf
rounding is "unbiased,"
which means it doesn't always round a trailing `.5' up, contrary
to naive expectations. In unbiased rounding, `.5' rounds to even,
rather than always up, so 1.5 rounds to 2 but 4.5 rounds to 4. This means
that if you are using a format that does rounding (e.g., "%.0f"
),
you should check what your system does. The following function does
traditional rounding; it might be useful if your awk's printf
does unbiased rounding:
# round.awk --- do normal rounding function round(x, ival, aval, fraction) { ival = int(x) # integer part, int() truncates # see if fractional part if (ival == x) # no fraction return x if (x < 0) { aval = -x # absolute value ival = int(aval) fraction = aval - ival if (fraction >= .5) return int(x) - 1 # -2.5 --> -3 else return int(x) # -2.3 --> -2 } else { fraction = x - ival if (fraction >= .5) return ival + 1 else return ival } } # test harness { print $0, round($0) } |
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