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Dima Kogan > feedgnuplot-1.24 > feedgnuplot


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feedgnuplot - Pipe-oriented frontend to Gnuplot


Simple plotting of stored data:

 $ seq 5 | awk '{print 2*$1, $1*$1}'
 2 1
 4 4
 6 9
 8 16
 10 25

 $ seq 5 | awk '{print 2*$1, $1*$1}' |
   feedgnuplot --lines --points --legend 0 "data 0" --title "Test plot" --y2 1

Simple real-time plotting example: plot how much data is received on the wlan0 network interface in bytes/second (uses bash, awk and Linux):

 $ while true; do sleep 1; cat /proc/net/dev; done |
   gawk '/wlan0/ {if(b) {print $2-b; fflush()} b=$2}' |
   feedgnuplot --lines --stream --xlen 10 --ylabel 'Bytes/sec' --xlabel seconds


This is a flexible, command-line-oriented frontend to Gnuplot. It creates plots from data coming in on STDIN or given in a filename passed on the commandline. Various data representations are supported, as is hardcopy output and streaming display of live data. A simple example:

 $ seq 5 | awk '{print 2*$1, $1*$1}' | feedgnuplot

You should see a plot with two curves. The awk command generates some data to plot and the feedgnuplot reads it in from STDIN and generates the plot. The awk invocation is just an example; more interesting things would be plotted in normal usage. No commandline-options are required for the most basic plotting. Input parsing is flexible; every line need not have the same number of points. New curves will be created as needed.

The most commonly used functionality of gnuplot is supported directly by the script. Anything not directly supported can still be done with the --extracmds and --curvestyle options. Arbitrary gnuplot commands can be passed in with --extracmds. For example, to turn off the grid, pass in --extracmds 'unset grid'. As many of these options as needed can be passed in. To add arbitrary curve styles, use --curvestyle curveID extrastyle. Pass these more than once to affect more than one curve. To apply an extra style to all the curves that lack an explicit --curvestyle, pass in --curvestyleall extrastyle.

Data formats

By default, each value present in the incoming data represents a distinct data point, as demonstrated in the original example above (we had 10 numbers in the input and 10 points in the plot). If requested, the script supports more sophisticated interpretation of input data

Domain selection

If --domain is passed in, the first value on each line of input is interpreted as the X-value for the rest of the data on that line. Without --domain the X-value is the line number, and the first value on a line is a plain data point like the others. Default is --nodomain. Thus the original example above produces 2 curves, with 1,2,3,4,5 as the X-values. If we run the same command with --domain:

 $ seq 5 | awk '{print 2*$1, $1*$1}' | feedgnuplot --domain

we get only 1 curve, with 2,4,6,8,10 as the X-values. As many points as desired can appear on a single line, but all points on a line are associated with the X-value at the start of that line.

Curve indexing

By default, each column represents a separate curve. This is fine unless sparse data is to be plotted. With the --dataid option, each point is represented by 2 values: a string identifying the curve, and the value itself. If we add --dataid to the original example:

 $ seq 5 | awk '{print 2*$1, $1*$1}' | feedgnuplot --dataid --autolegend

we get 5 different curves with one point in each. The first column, as produced by awk, is 2,4,6,8,10. These are interpreted as the IDs of the curves to be plotted. The --autolegend option adds a legend using the given IDs to label the curves. The IDs need not be numbers; generic strings are accepted. As many points as desired can appear on a single line. --domain can be used in conjunction with --dataid.

Multi-value style support

Depending on how gnuplot is plotting the data, more than one value may be needed to represent a single point. For example, the script has support to plot all the data with --circles. This requires a radius to be specified for each point in addition to the position of the point. Thus, when plotting with --circles, 2 numbers are read for each data point instead of 1. A similar situation exists with --colormap where each point contains the position and the color. There are other gnuplot styles that require more data (such as error bars), but none of these are directly supported by the script. They can still be used, though, by specifying the specific style with --curvestyle, and specifying how many extra values are needed for each point with --extraValuesPerPoint extra. --extraValuesPerPoint is ONLY needed for the styles not explicitly supported; supported styles set that variable automatically.

3D data

To plot 3D data, pass in --3d. --domain MUST be given when plotting 3D data to avoid domain ambiguity. If 3D data is being plotted, there are by definition 2 domain values instead of one (Z as a function of X and Y instead of Y as a function of X). Thus the first 2 values on each line are interpreted as the domain instead of just 1. The rest of the processing happens the same way as before.

Special data commands

Other than the raw data, 2 special commands are interpreted if they appear in the input. These are replot and clear. If a line of data begins with replot and we're plotting in realtime with --stream, the plot will be refreshed immediately. If a line of data begins with clear, the plot is cleared, to be re-filled with any data following the clear.

Real-time streaming data

To plot real-time data, pass in the --stream [refreshperiod] option. Data will then be plotted as it is received. The plot will be updated every refreshperiod seconds. If the period isn't specified, a 1Hz refresh rate is used. To refresh at specific intervals indicated by the data, set the refreshperiod to 0 or to 'trigger'. The plot will then only be refreshed when a data line 'replot' is received. This 'replot' command works in both triggered and timed modes, but in triggered mode, it's the only way to replot.

To plot only the most recent data (instead of all the data), --xlen windowsize can be given. This will create an constantly-updating, scrolling view of the recent past. windowsize should be replaced by the desired length of the domain window to plot, in domain units (passed-in values if --domain or line numbers otherwise).

Hardcopy output

The script is able to produce hardcopy output with --hardcopy outputfile. The output type can be inferred from the filename, if .ps, .eps, .pdf, .svg or .png is requested. If any other file type is requested, --terminal must be passed in to tell gnuplot how to make the plot.

Self-plotting data files

This script can be used to enable self-plotting data files. There are 2 ways of doing this: with a shebang (#!) or with inline perl data.

Self-plotting data with a #!

A self-plotting, executable data file data is formatted as

 $ cat data
 #!/usr/bin/feedgnuplot --lines --points
 2 1
 4 4
 6 9
 8 16
 10 25
 12 36
 14 49
 16 64
 18 81
 20 100
 22 121
 24 144
 26 169
 28 196
 30 225

This is the shebang (#!) line followed by the data, formatted as before. The data file can be plotted simply with

 $ ./data

The caveats here are that on Linux the whole #! line is limited to 127 charaters and that the full path to feedgnuplot must be given. The 127 character limit is a serious limitation, but this can likely be resolved with a kernel patch. I have only tried on Linux 2.6.

Self-plotting data with perl inline data

Perl supports storing data and code in the same file. This can also be used to create self-plotting files:

 $ cat
 use strict;
 use warnings;

 open PLOT, "| feedgnuplot --lines --points" or die "Couldn't open plotting pipe";
 while( <DATA> )
   my @xy = split;
   print PLOT "@xy\n";
 2 1
 4 4
 6 9
 8 16
 10 25
 12 36
 14 49
 16 64
 18 81
 20 100
 22 121
 24 144
 26 169
 28 196
 30 225

This is especially useful if the logged data is not in a format directly supported by feedgnuplot. Raw data can be stored after the __DATA__ directive, with a small perl script to manipulate the data into a useable format and send it to the plotter.


  --[no]domain         If enabled, the first element of each line is the
                       domain variable.  If not, the point index is used

  --[no]dataid         If enabled, each data point is preceded by the ID
                       of the data set that point corresponds to. This ID is
                       interpreted as a string, NOT as just a number. If not
                       enabled, the order of the point is used.

As an example, if line 3 of the input is "0 9 1 20" '--nodomain --nodataid' would parse the 4 numbers as points in 4 different curves at x=3

 '--domain --nodataid' would parse the 4 numbers as points in 3 different
   curves at x=0. Here, 0 is the x-variable and 9,1,20 are the data values

 '--nodomain --dataid' would parse the 4 numbers as points in 2 different
   curves at x=3. Here 0 and 1 are the data IDs and 9 and 20 are the
   data values

 '--domain --dataid' would parse the 4 numbers as a single point at
   x=0. Here 9 is the data ID and 1 is the data value. 20 is an extra
   value, so it is ignored. If another value followed 20, we'd get another
   point in curve ID 20

  --[no]3d             Do [not] plot in 3D. This only makes sense with --domain.
                       Each domain here is an (x,y) tuple

  --colormap           Show a colormapped xy plot. Requires extra data for the color.
                       zmin/zmax can be used to set the extents of the colors.
                       Automatically increments extraValuesPerPoint

  --stream [period]    Plot the data as it comes in, in realtime. If period is given,
                       replot every period seconds. If no period is given, replot at
                       1Hz. If the period is given as 0 or 'trigger', replot ONLY when
                       the incoming data dictates this . See the "Real-time streaming
                       data" section of the man page.

  --[no]lines          Do [not] draw lines to connect consecutive points
  --[no]points         Do [not] draw points
  --circles            Plot with circles. This requires a radius be specified for
                       each point. Automatically increments extraValuesPerPoint

  --xlabel xxx         Set x-axis label
  --ylabel xxx         Set y-axis label
  --y2label xxx        Set y2-axis label. Does not apply to 3d plots
  --zlabel xxx         Set y-axis label. Only applies to 3d plots

  --title  xxx         Set the title of the plot

  --legend curveID legend
                       Set the label for a curve plot. Use this option multiple times
                       for multiple curves. With --dataid, curveID is the ID. Otherwise,
                       it's the index of the curve, starting at 0

  --autolegend         Use the curve IDs for the legend. Titles given with --legend
                       override these

  --xlen xxx           When using --stream, sets the size of the x-window to plot.
                       Omit this or set it to 0 to plot ALL the data. Does not
                       make sense with 3d plots. Implies --monotonic

  --xmin  xxx          Set the range for the x axis. These are ignored in a
                       streaming plot
  --xmax  xxx          Set the range for the x axis. These are ignored in a
                       streaming plot
  --ymin  xxx          Set the range for the y axis.
  --ymax  xxx          Set the range for the y axis.
  --y2min xxx          Set the range for the y2 axis. Does not apply to 3d plots.
  --y2max xxx          Set the range for the y2 axis. Does not apply to 3d plots.
  --zmin  xxx          Set the range for the z axis. Only applies to 3d plots or colormaps.
  --zmax  xxx          Set the range for the z axis. Only applies to 3d plots or colormaps.

  --y2    xxx          Plot the data specified by this curve ID on the y2 axis.
                       Without --dataid, the ID is just an ordered 0-based index.
                       Does not apply to 3d plots. Can be passed multiple times, or passed a
                       comma-separated list

  --histogram  curveID
                       Set up a this specific curve to plot a histogram. The bin
                       width is given with the --binwidth option (assumed 1.0 if
                       omitted). --histogram does NOT touch the drawing style.
                       It is often desired to plot these with boxes, and this
                       MUST be explicitly requested with --curvestyleall 'with
                       boxes'. This works with --domain and/or --stream, but in
                       those cases the x-value is used ONLY to cull old data
                       because of --xlen or --monotonic. I.e. the x-values are
                       NOT drawn in any way. Can be passed multiple times, or passed a comma-
                       separated list
  --binwidth width     The width of bins when making histograms. This setting applies to ALL
                       histograms in the plot. Defaults to 1.0 if not given.
  --histstyle style    Normally, histograms are generated with the 'smooth freq'
                       gnuplot style. --histstyle can be used to select
                       different 'smooth' settings. Allowed are 'unique',
                       'cumulative' and 'cnormal'. 'unique' indicates whether a
                       bin has at least one item in it: instead of counting the
                       items, it'll always report 0 or 1. 'cumulative' is the
                       integral of the "normal" histogram. 'cnormal' is like
                       'cumulative', but rescaled to end up at 1.0.

  --curvestyle curveID style
                       Additional styles per curve. With --dataid, curveID is
                       the ID. Otherwise, it's the index of the curve, starting
                       at 0. Use this option multiple times for multiple curves.
                       --curvestylall does NOT apply to curves that have a

  --curvestyleall xxx  Additional styles for all curves that have no --curvestyle

  --extracmds xxx      Additional commands. These could contain extra global styles
                       for instance. Can be passed multiple times.

  --square             Plot data with aspect ratio 1. For 3D plots, this controls the
                       aspect ratio for all 3 axes

  --square_xy          For 3D plots, set square aspect ratio for ONLY the x,y axes

  --hardcopy xxx       If not streaming, output to a file specified here. Format
                       inferred from filename, unless specified by --terminal
  --terminal xxx       String passed to 'set terminal'. No attempts are made to
                       validate this. --hardcopy sets this to some sensible
                       defaults if --hardcopy is given .png, .pdf, .ps, .eps or
                       .svg. If any other file type is desired, use both
                       --hardcopy and --terminal

  --maxcurves xxx      The maximum allowed number of curves. This is 100 by default,
                       but can be reset with this option. This exists purely to
                       prevent perl from allocating all of the system's memory when
                       reading bogus data

  --monotonic          If --domain is given, checks to make sure that the x-
                       coordinate in the input data is monotonically increasing.
                       If a given x-variable is in the past, all data currently
                       cached for this curve is purged. Without --monotonic, all
                       data is kept. Does not make sense with 3d plots.
                       No --monotonic by default.

  --extraValuesPerPoint xxx
                       How many extra values are given for each data point. Normally this
                       is 0, and does not need to be specified, but sometimes we want
                       extra data, like for colors or point sizes or error bars, etc.
                       feedgnuplot options that require this (colormap, circles)
                       automatically set it. This option is ONLY needed if unknown styles are
                       used, with --curvestyleall for instance

  --dump               Instead of printing to gnuplot, print to STDOUT. Very useful for
                       debugging. It is possible to send the output produced this way to
                       gnuplot directly.

  --geometry           If using X11, specifies the size, position of the plot window

  --version            Print the version and exit


This program is originally based on the script from Thanassis Tsiodras. It is available from his site at



Dima Kogan, <>


Copyright 2011-2012 Dima Kogan.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See for more information.

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