Re: printf exact field width of floating point number

The format specifier %8.6f says place the number in an 8 char wide space and include 6 digits of decimals. One of the two extra spaces is occupied by the decimal point; the last is used for the integer part of the value. Which in this case will be restricted to a single digit before the field width will be overridden.

A specifier of %6.6f doesn;t make much sense because it leaves no room for the decimal point or integer part of the number.

For the most flexible representation, use %12.6g (or larger) which will make a reasonable fist of displaying a fairly wide range of values in a semi consistant fashion:

[0] Perl> printf "%12.6g\n", $_ for map{ "1.23456e$_" } -12 .. +12;;
1.23456e-012
1.23456e-011
1.23456e-010
1.23456e-009
1.23456e-008
1.23456e-007
1.23456e-006
1.23456e-005
 0.000123456
  0.00123456
   0.0123456
    0.123456
     1.23456
     12.3456
     123.456
     1234.56
     12345.6
      123456
1.23456e+006
1.23456e+007
1.23456e+008
1.23456e+009
1.23456e+010
1.23456e+011
1.23456e+012
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The floating point formatting by sprintf has always -- going way back to the earliest of C compilers -- left a lot to be desired.

You might also find the threads at Engineering FP notation & sprintf and Display floating point numbers in compact, fixed-width format of interest.

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Re^2: printf exact field width of floating point number by flipper (Beadle) on Mar 28, 2012 at 09:56 UTC
Yuck! Thanks explains perfectly, thank you!	[reply]
Re^2: printf exact field width of floating point number by aaron_baugher (Curate) on Mar 28, 2012 at 20:32 UTC
The floating point formatting by sprintf has always -- going way back to the earliest of C compilers -- left a lot to be desired. Indeed. I don't use `printf` that often, so I tend to forget that the number preceding the decimal point specifies how many total characters there are, instead of how many digits before the decimal point, which seems more intuitive to me. So I too often try something like `%3.2f`, expecting that to handle numbers like 123.45, before remembering that the first digit has to include the length of the second (and the decimal point). Aaron B. My Woefully Neglected Blog, where I occasionally mention Perl.	[reply] [d/l] [select]