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feedgnuplot - General purpose pipe-oriented plotting tool


Simple plotting of piped 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
               --unset grid --terminal 'dumb 80,40' --exit

                                  Test plot

  10 +-----------------------------------------------------------------+ 25
     |       +        +       +       +       +        +       +    *##|
     |                                                  data 0 ***A*#* |
     |                                                          ** #   |
   9 |-+                                                      ** ##    |
     |                                                      **  #      |
     |                                                    **   #       |
     |                                                  **   ##      +-| 20
   8 |-+                                               A    #          |
     |                                               **    #           |
     |                                             **    ##            |
     |                                           **     #              |
     |                                         **      B               |
   7 |-+                                     **      ##                |
     |                                     **      ##                +-| 15
     |                                   **       #                    |
     |                                 **       ##                     |
   6 |-+                             *A       ##                       |
     |                             **       ##                         |
     |                           **        #                           |
     |                         **        ##                          +-| 10
   5 |-+                     **        ##                              |
     |                     **        #B                                |
     |                   **        ##                                  |
     |                 **        ##                                    |
   4 |-+              A       ###                                      |
     |              **      ##                                         |
     |            **      ##                                         +-| 5
     |          **      ##                                             |
     |        **    ##B#                                               |
   3 |-+    **  ####                                                   |
     |    **####                                                       |
     |  ####                                                           |
     |##     +        +       +       +       +        +       +       |
   2 +-----------------------------------------------------------------+ 0
     1      1.5       2      2.5      3      3.5       4      4.5      5

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 options such as --set, --extracmds --style, etc. Arbitrary gnuplot commands can be passed in with --extracmds. For example, to turn off the grid, you can pass in --extracmds 'unset grid'. Commands --set and --unset exists to provide nicer syntax, so this is equivalent to passing --unset grid. As many of these options as needed can be passed in. To add arbitrary curve styles, use --style 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 --style, pass in --styleall extrastyle. In the most common case, the extra style is with something. To support this more simply, you can pass in --with something instead of --styleall 'with something'. --styleall and --with are mutually exclusive. Furthermore any curve-specific --style overrides the global --styleall or --with setting.

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

We index the curves in one of 3 ways: sequentially, explicitly with a --dataid or by --vnlog headers.

By default, each column represents a separate curve. The first column (after any domain) is curve 0. The next one is curve 1 and so on. 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.

If we're plotting vnlog data ( then we can get the curve IDs from the vnlog header. Vnlog is a trivial data format where lines starting with # are comments and the first comment contains column labels. If we have such data, feedgnuplot --vnlog can interpret these column labels if the vnlog perl modules are available.

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 or --vnlog.

Multi-value style support

Depending on how gnuplot is plotting the data, more than one value may be needed to represent the range of a single point. Basic 2D plots have 2 numbers representing each point: 1 domain and 1 range. But if plotting with --circles, for instance, then there's an extra range value: the radius. Many other gnuplot styles require more data: errorbars, variable colors (with points palette), variable sizes (with points ps variable), labels and so on. The feedgnuplot tool itself does not know about all these intricacies, but they can still be used, by specifying the specific style with --style, and specifying how many values are needed for each point with any of --rangesizeall, --tuplesizeall, --rangesize, --tuplesize. These options are required only for styles not explicitly supported by feedgnuplot; supported styles do the right thing automatically.

Specific example: if making a 2d plot of y error bars, the exact format can be queried by running gnuplot and invoking help yerrorbars. This tells us that there's a 3-column form: x y ydelta and a 4-column form: x y ylow yhigh. With 2d plots feedgnuplot will always output the 1-value domain x, so the rangesize is 2 and 3 respectively. Thus the following are equivalent:

 $ echo '1 2 0.3
         2 3 0.4
         3 4 0.5' | feedgnuplot --domain --rangesizeall 2 --with 'yerrorbars'

 $ echo '1 2 0.3
         2 3 0.4
         3 4 0.5' | feedgnuplot --domain --tuplesizeall 3 --with 'yerrorbars'

 $ echo '1 2 1.7 2.3
         2 3 2.6 3.4
         3 4 3.5 4.5' | feedgnuplot --domain --rangesizeall 3 --with 'yerrorbars'

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.

Time/date data

If the input data domain is a time/date, this can be interpreted with --timefmt. This option takes a single argument: the format to use to parse the data. The format is documented in 'set timefmt' in gnuplot, although the common flags that strftime understands are generally supported. The backslash sequences in the format are not supported, so if you want a tab, put in a tab instead of \t. Whitespace in the format is supported. When this flag is given, some other options act a little bit differently:

Using this option changes both the way the input is parsed and the way the x-axis tics are labelled. Gnuplot tries to be intelligent in this labelling, but it doesn't always do what the user wants. The labelling can be controlled with the gnuplot set format command, which takes the same type of format string as --timefmt. Example:

 $ sar 1 -1 |
   awk '$1 ~ /..:..:../ && $8 ~/^[0-9\.]*$/ {print $1,$8; fflush()}' |
   feedgnuplot --stream --domain
                --lines --timefmt '%H:%M:%S'
                --set 'format x "%H:%M:%S"'

This plots the 'idle' CPU consumption against time.

Note that while gnuplot supports the time/date on any axis, feedgnuplot currently supports it only as the x-axis domain. This may change in the future.

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. Look in "Special data commands" for more information.

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). If the domain is a time/date via --timefmt, then windowsize is and integer in seconds. If we're plotting a histogram, then --xlen causes a histogram over a moving window to be computed. The subtlely here is that with a histogram you don't actually see the domain since only the range is analyzed. But the domain is still there, and can be utilized with --xlen. With --xlen we can plot only histograms or only non-histograms.

Special data commands

If we are reading streaming data, the input stream can contain special commands in addition to the raw data. Feedgnuplot looks for these at the start of every input line. If a command is detected, the rest of the line is discarded. These commands are


This command refreshes the plot right now, instead of waiting for the next refresh time indicated by the timer. This command works in addition to the timed refresh, as indicated by --stream [refreshperiod].


This command clears out the current data in the plot. The plotting process continues, however, to any data following the clear.


This command causes feedgnuplot to exit.

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. If --terminal is passed in, then the --hardcopy argument only provides the output filename.

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 characters 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.



Basic plotting of piped 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

Realtime plot of network throughput

Looks at wlan0 on 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

Realtime plot of battery charge in respect to time

Uses the result of the acpi command.

 $ while true; do acpi; sleep 15; done |
   perl -nE 'BEGIN{ $| = 1; } /([0-9]*)%/; say join(" ", time(), $1);' |
   feedgnuplot --stream --ymin 0 --ymax 100 --lines --domain --xlabel 'Time' --timefmt '%s' --ylabel "Battery charge (%)"

Realtime plot of temperatures in an IBM Thinkpad

Uses /proc/acpi/ibm/thermal, which reports temperatures at various locations in a Thinkpad.

 $ while true; do cat /proc/acpi/ibm/thermal | awk '{$1=""; print}' ; sleep 1; done |
   feedgnuplot --stream --xlen 100 --lines --autolegend --ymax 100 --ymin 20 --ylabel 'Temperature (deg C)'

Plotting a histogram of file sizes in a directory, granular to 10MB

 $ ls -l | awk '{print $5/1e6}' |
   feedgnuplot --histogram 0
     --binwidth 10
     --ymin 0 --xlabel 'File size (MB)' --ylabel Frequency

Plotting a live histogram of the ping round-trip times for the past 20 seconds

 $ ping -A -D |
   perl -anE 'BEGIN { $| = 1; }
              $F[0] =~ s/[\[\]]//g or next;
              $F[7] =~ s/.*=//g    or next;
              say "$F[0] $F[7]"' |
   feedgnuplot --stream --domain --histogram 0 --binwidth 10 \
               --xlabel 'Ping round-trip time (s)'  \
               --ylabel Frequency --xlen 20

Plotting points on top of an existing image

This can be done with --image:

 $ <
   feedgnuplot --points --domain --image "image.png"

or with --equation:

 $ <
   feedgnuplot --points --domain
     --equation '"image.png" binary filetype=auto flipy with rgbimage'
     --set 'yrange [:] reverse'

The --image invocation is a convenience wrapper for the --equation version. Finer control is available with --equation.

Here an existing image is given to gnuplot verbatim, and data to plot on top of it is interpreted by feedgnuplot as usual. flipy is useful here because usually the y axis points up, but when looking at images, this is usually reversed: the origin is the top-left pixel.


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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