allow --units-length to reserve label space even when --y-grid=none is in effect...

[rrdtool.git] / doc / rrdgraph.pod

=head1 NAME

rrdgraph - Round Robin Database tool grapher functions

=head1 SYNOPSIS

B<rrdtool graph> I<filename>
[I<L<option|rrdgraph/OPTIONS>> ...]
[I<L<data definition|rrdgraph_data/DEF>> ...]
[I<L<data calculation|rrdgraph_data/CDEF>> ...]
[I<L<variable definition|rrdgraph_data/VDEF>> ...]
[I<L<graph element|rrdgraph_graph/GRAPH>> ...]
[I<L<print element|rrdgraph_graph/PRINT>> ...]

=head1 DESCRIPTION

The B<graph> function of B<RRDtool> is used to present the
data from an B<RRD> to a human viewer.  Its main purpose is to
create a nice graphical representation, but it can also generate
a numerical report.

=head1 OVERVIEW

B<rrdtool graph> needs data to work with, so you must use one or more
B<L<data definition|rrdgraph_data/DEF>> statements to collect this
data.  You are not limited to one database, it's perfectly legal to
collect data from two or more databases (one per statement, though).

If you want to display averages, maxima, percentiles, etcetera
it is best to collect them now using the
B<L<variable definition|rrdgraph_data/VDEF>> statement.
Currently this makes no difference, but in a future version
of rrdtool you may want to collect these values before consolidation.

The data fetched from the B<RRA> is then B<consolidated> so that
there is exactly one datapoint per pixel in the graph. If you do
not take care yourself, B<RRDtool> will expand the range slightly
if necessary. Note, in that case the first and/or last pixel may very
well become unknown!

Sometimes data is not exactly in the format you would like to display
it. For instance, you might be collecting B<bytes> per second, but
want to display B<bits> per second. This is what the B<L<data
calculation|rrdgraph_data/CDEF>> command is designed for. After
B<consolidating> the data, a copy is made and this copy is modified
using a rather powerful B<L<RPN|rrdgraph_rpn/>> command set.

When you are done fetching and processing the data, it is time to
graph it (or print it).  This ends the B<rrdtool graph> sequence.

=head1 OPTIONS

=over 4

=item filename

The name and path of the graph to generate. It is recommended to
end this in C<.png>, C<.svg> or C<.eps>, but B<RRDtool> does not enforce this.

I<filename> can be 'C<->' to send the image to C<stdout>. In
this case, no other output is generated.

=item Time range

[B<-s>|B<--start> I<time>]
[B<-e>|B<--end> I<time>]
[B<-S>|B<--step> I<seconds>]

The start and end of the time series you would like to display, and which
B<RRA> the data should come from.  Defaults are: 1 day ago until
now, with the best possible resolution. B<Start> and B<end> can
be specified in several formats, see
L<AT-STYLE TIME SPECIFICATION|rrdfetch/> and L<rrdgraph_examples>.
By default, B<rrdtool graph> calculates the width of one pixel in
the time domain and tries to get data from an B<RRA> with that
resolution.  With the B<step> option you can alter this behaviour.
If you want B<rrdtool graph> to get data at a one-hour resolution
from the B<RRD>, set B<step> to 3'600. Note: a step smaller than
one pixel will silently be ignored.

=item Labels

[B<-t>|B<--title> I<string>]
[B<-v>|B<--vertical-label> I<string>]

A horizontal string at the top of the graph and/or a vertically
placed string at the left hand side of the graph.

=item Size

[B<-w>|B<--width> I<pixels>]
[B<-h>|B<--height> I<pixels>]
[B<-j>|B<--only-graph>]

The width and height of the B<canvas> (the part of the graph with
the actual data and such). This defaults to 400 pixels by 100 pixels.

If you specify the B<--only-graph> option and set the height E<lt> 32
pixels you will get a tiny graph image (thumbnail) to use as an icon
for use in an overview, for example. All labeling will be stripped off
the graph.

=item Limits

[B<-u>|B<--upper-limit> I<value>]
[B<-l>|B<--lower-limit> I<value>]
[B<-r>|B<--rigid>]

By default the graph will be autoscaling so that it will adjust the
y-axis to the range of the data. You can change this behaviour by
explicitly setting the limits. The displayed y-axis will then range at
least from B<lower-limit> to B<upper-limit>. Autoscaling will still
permit those boundaries to be stretched unless the B<rigid> option is
set.

[B<-A>|B<--alt-autoscale>]

Sometimes the default algorithm for selecting the y-axis scale is not
satisfactory. Normally the scale is selected from a predefined
set of ranges and this fails miserably when you need to graph something
like C<260 + 0.001 * sin(x)>. This option calculates the minimum and
maximum y-axis from the actual minimum and maximum data values. Our example
would display slightly less than C<260-0.001> to slightly more than
C<260+0.001> (this feature was contributed by Sasha Mikheev).

[B<-M>|B<--alt-autoscale-max>]

Where C<--alt-autoscale> will modify both the absolute maximum AND minimum
values, this option will only affect the maximum value. The minimum
value, if not defined on the command line, will be 0. This option can
be useful when graphing router traffic when the WAN line uses compression,
and thus the throughput may be higher than the WAN line speed.

[B<-N>|B<--no-gridfit>]

In order to avoid anti-aliasing effects gridlines are placed on
integer pixel values. This is by default done by extending
the scale so that gridlines happens to be spaced using an
integer number of pixels and also start on an integer pixel value.
This might extend the scale too much for some logarithmic scales
and for linear scales where B<--alt-autoscale> is needed.
Using B<--no-gridfit> disables modification of the scale.

=item Grid

=over 4

=item X-Axis

[B<-x>|B<--x-grid> I<GTM>B<:>I<GST>B<:>I<MTM>B<:>I<MST>B<:>I<LTM>B<:>I<LST>B<:>I<LPR>B<:>I<LFM>]

[B<-x>|B<--x-grid> B<none>]

The x-axis label is quite complex to configure. If you don't have
very special needs it is probably best to rely on the autoconfiguration
to get this right. You can specify the string C<none> to suppress the grid
and labels altogether.

The grid is defined by specifying a certain amount of time in the I<?TM>
positions. You can choose from C<SECOND>, C<MINUTE>, C<HOUR>, C<DAY>,
C<WEEK>, C<MONTH> or C<YEAR>. Then you define how many of these should
pass between each line or label.  This pair (I<?TM:?ST>) needs to be
specified for the base grid (I<G??>), the major grid (I<M??>) and the
labels (I<L??>). For the labels you also must define a precision
in I<LPR> and a I<strftime> format string in I<LFM>.  I<LPR> defines
where each label will be placed. If it is zero, the label will be
placed right under the corresponding line (useful for hours, dates
etcetera).  If you specify a number of seconds here the label is
centered on this interval (useful for Monday, January etcetera).

 --x-grid MINUTE:10:HOUR:1:HOUR:4:0:%X

This places grid lines every 10 minutes, major grid lines every hour,
and labels every 4 hours. The labels are placed under the major grid
lines as they specify exactly that time.

 --x-grid HOUR:8:DAY:1:DAY:1:0:%A

This places grid lines every 8 hours, major grid lines and labels
each day. The labels are placed exactly between two major grid lines
as they specify the complete day and not just midnight.

=item Y-Axis

[B<-y>|B<--y-grid> I<grid step>B<:>I<label factor>]

[B<-y>|B<--y-grid> B<none>]

Y-axis grid lines appear at each I<grid step> interval.  Labels are
placed every I<label factor> lines.  You can specify C<-y none> to
suppress the grid and labels altogether.  The default for this option is
to automatically select sensible values.

If you have set --y-grid to 'none' not only the labels get supressed, also
the space reserved for the labels is removed. You can still add space
manually if you use the --units-length command to explicitly reserve space.

[B<-Y>|B<--alt-y-grid>]

Place the Y grid dynamically based on the graph's Y range. The algorithm
ensures that you always have a grid, that there are enough but not too many
grid lines, and that the grid is metric. That is the grid lines are placed
every 1, 2, 5 or 10 units. This parameter will also ensure that you get
enough decimals displayed even if your graph goes from 69.998 to 70.001. 
(contributed by Sasha Mikheev).

[B<-o>|B<--logarithmic>]

Logarithmic y-axis scaling.

[B<-X>|B<--units-exponent> I<value>]

This sets the 10**exponent scaling of the y-axis values. Normally,
values will be scaled to the appropriate units (k, M, etc.).  However,
you may wish to display units always in k (Kilo, 10e3) even if the data
is in the M (Mega, 10e6) range, for instance. Value should be an
integer which is a multiple of 3 between -18 and 18 inclusively.  It is
the exponent on the units you wish to use. For example, use 3 to
display the y-axis values in k (Kilo, 10e3, thousands), use -6 to
display the y-axis values in u (Micro, 10e-6, millionths).  Use a value
of 0 to prevent any scaling of the y-axis values.

This option is very effective at confusing the heck out of the default
rrdtool autoscaler and grid painter. If rrdtool detects that it is not
successful in labeling the graph under the given circumstances, it will switch
to the more robust B<--alt-y-grid> mode.

[B<-L>|B<--units-length> I<value>]

How many digits should rrdtool assume the y-axis labels to be? You
may have to use this option to make enough space once you start
fideling with the y-axis labeling.

[B<--units=si>]

With this option y-axis values on logarithmic graphs will be scaled to 
the appropriate units (k, M, etc.) instead of using exponential notation.
Note that for linear graphs, SI notation is used by default.

=back

=item Miscellaneous

[B<-z>|B<--lazy>]

Only generate the graph if the current graph is out of date or not
existent.

[B<-f>|B<--imginfo> I<printfstr>]

After the image has been created, the graph function uses printf
together with this format string to create output similar to the PRINT
function, only that the printf function is supplied with the parameters
I<filename>, I<xsize> and I<ysize>. In order to generate an B<IMG> tag
suitable for including the graph into a web page, the command line
would look like this:

 --imginfo '<IMG SRC="/img/%s" WIDTH="%lu" HEIGHT="%lu" ALT="Demo">'

[B<-c>|B<--color> I<COLORTAG>#I<rrggbb>[I<aa>]]

Override the default colors for the standard elements of the graph. The
I<COLORTAG> is one of C<BACK> background, C<CANVAS> for the background of
the actual graph, C<SHADEA> for the left and top border, C<SHADEB> for the
right and bottom border, C<GRID>, C<MGRID> for the major grid, C<FONT> for
the color of the font, C<AXIS> for the axis of the graph, C<FRAME> for the
line around the color spots and finally C<ARROW> for the arrow head pointing
up and forward. Each color is composed out of three hexadecimal numbers
specifying its rgb color component (00 is off, FF is maximum) of red, green
and blue. Optionally you may add another hexadecimal number specifying the
transparency (FF is solid). You may set this option several times to alter
multiple defaults.

A green arrow is made by: C<--color ARROW#00FF00>

[B<--zoom> I<factor>]

Zoom the graphics by the given amount. The factor must be E<gt> 0

[B<-n>|B<--font> I<FONTTAG>B<:>I<size>B<:>[I<font>]]

This lets you customize which font to use for the various text
elements on the RRD graphs. C<DEFAULT> sets the default value for all
elements, C<TITLE> for the title, C<AXIS> for the axis labels, C<UNIT>
for the vertical unit label, C<LEGEND> for the graph legend.

Use Times for the title: C<--font TITLE:13:/usr/lib/fonts/times.ttf>

If you do not give a font string you can modify just the sice of the default font:
C<--font TITLE:13:>.

If you specify the size 0 then you can modify just the font without touching
the size. This is especially usefull for altering the default font without
resetting the default fontsizes: C<--font DEFAULT:0:/usr/lib/fonts/times.ttf>.

RRDtool comes with a preset default font. You can set the environment
variable C<RRD_DEFAULT_FONT> if you want to change this.

Truetype fonts are only supported for PNG output. See below.

[B<-R>|B<--font-render-mode> {I<normal>,I<light>,I<mono>}]

This lets you customize the strength of the font smoothing,
or disable it entirely using I<mono>. By default, I<normal>
font smoothing is used.

[B<-B>|B<--font-smoothing-threshold> I<size>]

This specifies the largest font size which will be rendered
bitmapped, that is, without any font smoothing. By default,
no text is rendered bitmapped.

[B<-E>|B<--slope-mode>]

RRDtool graphs are composed of stair case curves by default. This is in line with
the way RRDtool calculates its data. Some people favor a more 'organic' look
for their graphs even though it is not all that true.

[B<-a>|B<--imgformat> B<PNG>|B<SVG>|B<EPS>|B<PDF>]

Image format for the generated graph. For the vector formats you can
choose among the standard Postscript fonts Courier-Bold,
Courier-BoldOblique, Courier-Oblique, Courier, Helvetica-Bold,
Helvetica-BoldOblique, Helvetica-Oblique, Helvetica, Symbol,
Times-Bold, Times-BoldItalic, Times-Italic, Times-Roman, and ZapfDingbats.

[B<-i>|B<--interlaced>]

If images are interlaced they become visible on browsers more quickly.

[B<-g>|B<--no-legend>]

Suppress generation of the legend; only render the graph.

[B<-F>|B<--force-rules-legend>]

Force the generation of HRULE and VRULE legends even if those HRULE or
VRULE will not be drawn because out of graph boundaries (mimics
behaviour of pre 1.0.42 versions).

[B<-T>|B<--tabwidth> I<value>]

By default the tab-width is 40 pixels, use this option to change it.

[B<-b>|B<--base> I<value>]

If you are graphing memory (and NOT network traffic) this switch
should be set to 1024 so that one Kb is 1024 byte. For traffic
measurement, 1 kb/s is 1000 b/s.

[B<-W>|B<--watermark> I<string>]

Adds the given string as a watermark, horizontally centred, at the bottom 
of the graph.

=item Data and variables

B<DEF:>I<vname>B<=>I<rrdfile>B<:>I<ds-name>B<:>I<CF>[B<:step=>I<step>][B<:start=>I<time>][B<:end=>I<time>]

B<CDEF:>I<vname>B<=>I<RPN expression>

B<VDEF:>I<vname>B<=>I<RPN expression>

You need at least one B<DEF> statement to generate anything. The
other statements are useful but optional.
See L<rrdgraph_data> and L<rrdgraph_rpn> for the exact format.

=item Graph and print elements

You need at least one graph element to generate an image and/or
at least one print statement to generate a report.
See L<rrdgraph_graph> for the exact format.

=back

=head1 SEE ALSO

L<rrdgraph> gives an overview of how B<rrdtool graph> works.
L<rrdgraph_data> describes B<DEF>,B<CDEF> and B<VDEF> in detail.
L<rrdgraph_rpn> describes the B<RPN> language used in the B<?DEF> statements.
L<rrdgraph_graph> page describes all of the graph and print functions.

Make sure to read L<rrdgraph_examples> for tipsE<amp>tricks.

=head1 AUTHOR

Program by Tobias Oetiker E<lt>tobi@oetiker.chE<gt>

This manual page by Alex van den Bogaerdt E<lt>alex@ergens.op.het.netE<gt>