[rrd-users] Re: RRD graph formatting

[Haroon Rafique]

On Today at 2:10pm, RN=>Robert Nelson <rnelson at windchannel.com> wrote:

RN> Hello,
RN> 
RN> I was wondering if someone could explain to me the difference between 
RN> %le, %lf, and %lg, and other formatting characters - or point me to 
RN> the document to look in. I can't seem to find anything on the web page 
RN> or in the man pages to describe this. Thanks.
RN> 

Hi Rob,

I haven't seen a reply so far. From:
	man 3 printf
on my machine (Gentoo Linux), I get:

       e,E    The double argument is rounded and converted in the style 
              [-]d.ddde<B1>dd where there is one digit before the 
              decimal-point character and the number of digits after it is 
              equal to the pre cision; if the precision is missing, it is 
              taken as 6;  if the precision is zero, no decimal-point 
              character appears.  An E conversion uses the letter E 
              (rather than e)  to introduce the exponent.  The exponent 
              always contains at least two digits; if the value is zero, 
              the exponent is 00.

       f,F    The double argument is rounded and converted to decimal 
              notation in the style [-]ddd.ddd, where the number of digits 
              after the decimal-point character is equal to the precision 
              specification.  If the precision is missing, it is taken as 
              6; if the precision is explicitly zero, no decimal-point 
              character appears.  If a decimal point appears, at least one 
              digit appears before it.  (The SUSv2 does not know about F 
              and says that character string representations for infinity 
              and NaN may be made available.  The C99 standard specifies 
              `[-]inf' or `[-]infinity' for infinity, and a string 
              starting with `nan' for NaN, in the case of f con- version, 
              and `[-]INF' or `[-]INFINITY' or `NAN*' in the case of F 
              conversion.)

       g,G    The double argument is converted in style f or e (or F or E 
              for G conversions).  The precision specifies the number of 
              signifi- cant digits.  If the precision is missing, 6 digits 
              are given;  if the precision is zero, it is treated as 1.  
              Style e is used if the exponent from its conversion is less 
              than -4 or greater than or equal to the precision.  
              Trailing zeros are removed from the fractional part of the 
              result; a decimal point appears only if it is followed by at 
              least one digit.

Here's sample output from my /usr/bin/printf program (part of coreutils):

$ printf %lf 0.0
0.000000
$ printf %le 0.0
0.000000e+00
$ printf %lg 0.0
0

In my rrd graphs, I mostly use %lf followed by a space followed by %s. 
>From man rrdgraph:

	 If an additional '%s' is found AFTER the marker, the value will
         be scaled and an appropriate SI magnitude unit will be printed 
         in place of the '%s' marker.

Cheers,
--
Haroon Rafique
<haroon.rafique at utoronto.ca>

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