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FEEDGNUPLOT(1) User Contributed Perl Documentation FEEDGNUPLOT(1)


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

Here we asked for ASCII plotting, which is useful for documentation.

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. For a tutorial and a gallery please see the guide at <>

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", "--cmds" "--style", etc. Arbitrary gnuplot commands can be passed in with "--cmds". For example, to turn off the grid, you can pass in "--cmds '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:

  • "--xlen" and "--binwidth" are integers in seconds
  • "--xmin" and "--xmax" must use the format passed in to "--timefmt"

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.

'using' expressions

We just described how feedgnuplot parses its input data. When passing this data to gnuplot, each curve is sent independently. The domain appears in the leading columns followed by "--rangesize" columns to complete each row. Without "--domain", feedgnuplot explicitly writes out sequential integers. gnuplot then knows how many values it has for each point, and it knows which style we're using, so it's able to interpret the data appropriately, and to make the correct plot.

As an example, if gnuplot is passed 2 columns of data, and it is plotting "with points", it will use column 1 for the x coordinate and column 2 for the y coordinate. This is the default behavior, but the meaning of each column can be controlled via a "using" expression in gnuplot (not feedgnuplot; keep reading). The default is sequential integers, so this example uses "using 1:2" by default. We can flip the meaning of the columns by passing "using 2:1". Arbitrary expressions may be specified by enclosing each field in "()", and using "$" to denote each data column. So to use the 2nd column as the x coordinate and the sum of the two columns as the y coordinate, "using 2:($1+$2)" is passed. Furthermore, the number of columns can vary. For instance gnuplot can read the same two columns of data, but produce a plot with the extra column encoding the sum as the color: "using 1:2:($1+$2) with points palette". Please see the gnuplot documentation for lots of detail.

That's how gnuplot works. Most of the time, feedgnuplot doesn't pass any "using" expressions at all, and gnuplot does the default thing. But if we want to do something fancy, feedgnuplot supports "--using curveID expression" and "--usingall expression". So we can plot a parabola:

  seq 100 | feedgnuplot --lines --usingall '1:($2*$2)'

This is powerful, but there are some things to keep in mind:

  • "--using" overrides whatever "using" expression feedgnuplot was going to pass. feedgnuplot passes a "using" expression only if "--histogram" or "--timefmt" or "--xticlabels" are given. So if "--using" is given together with any of these, the user must take care to do the right thing (whatever that means at that time).
  • The "--tuplesize" controls the data passed to feedgnuplot and the data then passed to gnuplot. It does not directly control how gnuplot eventually interprets the data: "--using" does that. So for instance we can plot color-coded points:

      seq 10 | feedgnuplot --with 'points pt 7 palette' --usingall '1:2:2'

    Here feedgnuplot read 1 column of data. It defauled to "--tuplesize 2", so it passed 2 columns of data to gnuplot. gnuplot then produced 3 values for each point, and plotted them as indicated with the "points palette" style.

  • You always need a column of data to generate a curve. You might want to use a "using" expression to plot a time series and its cumulative integral. The "using" expression can compute the integral, but you must pass in the data twice; once for each curve to plot:

      seq 100 |                           \
        awk '{print $1,$1}' |             \
        feedgnuplot                       \
          --cmds 'sum=0'                  \
          --cmds 'accum(x) = (sum=sum+x)' \
          --using 1 '1:(accum($2))'       \
          --lines --y2 1

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, .png or .gp 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.

The .gp output is special. Instead of asking gnuplot to plot to a particular terminal, writing to a .gp simply dumps a self-executable gnuplot script into the given file. This is similar to what "--dump" does, but writes to a file, and makes sure that the file can be self-executing.

Self-plotting data files

This script can be used to enable self-plotting data files. There are several 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 gnuplot

Running "feedgnuplot --hardcopy ...." will create a self-executable gnuplot script in ""

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" then

  • "--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
  • "--vnlog"

    Vnlog is a trivial data format where lines starting with "#" are comments and the first comment contains column labels. Some tools for working with such data are available from the "vnlog" project: <>. With the "vnlog" perl modules installed, we can read the vnlog column headers with "feedgnuplot --vnlog". This replaces "--dataid", and we can do all the normal things with these headers. For instance "feedgnuplot --vnlog --autolegend" will generate plot legends for each column in the vnlog, using the vnlog column label in the legend.

  • "--[no]3d"

    Do [not] plot in 3D. This only makes sense with "--domain". Each domain here is an (x,y) tuple

  • --"timefmt [format]"

    Interpret the X data as a time/date, parsed with the given format

  • "--colormap"

    This is a legacy option used to who a colormapped xy plot. It does:

    - Adds "palette" to "--curvestyleall"

    - Adds 1 to the default "--tuplesize" (if "--tuplesizeall" is not given

    - Uses "--zmin", "--zmax" to set the colorbar range

    It's clearer to set the relevant options explicitly, but "--colormap" still exists for compatibility

  • "--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 sets the "--rangesize"/"--tuplesize". "Not" supported for 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". 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.

  • "--xmin/xmax/x2min/x2max/ymin/ymax/y2min/y2max/zmin/zmax xxx"

    Set the range for the given axis. These x-axis bounds are ignored in a streaming plot. The x2/y2-axis bounds do not apply in 3d plots. The z-axis bounds apply only to 3d plots or colormaps. Note that there is no "--xrange" to set both sides at once or "--xinv" to flip the axis around: anything more than the basics supported in this option is clearly obtainable by talking to gnuplot, for instance "--set 'xrange [20:10]'" to set the given inverted bounds.

  • "--xlabel/x2label/ylabel/y2label/zlabel/cblabel xxx"

    Label the given axis. The x2/y2-axis labels do not apply to 3d plots while the z-axis label applies only to 3d plots. The "cblabel" applies to the colorbar, if there is one.

  • "--x2/--y2/--x1y2/--x2y1/--x2y2 xxx"

    By default data is plotted against the x1 and y1 axes (the left and bottom one respectively). If we want a particular curve plotted against a different axis, we can specify that with these options. You pass "--AXIS ID" where "AXIS" defines the axis ("x2" or "y2" or "x1y2" or "x2y1" or "x2y2") and the "ID" is the curve ID. "--x2" is a synonym for "--x2y1" and "--y2" is a synonym for "--x1y2". The curve ID is an ordered 0-based index or a specific ID if "--dataid" or "--vnlog". None of these apply to 3d plots. Can be passed multiple times for different curve IDs, multiple IDs can be passed in as a comma-separated list. By default the curves plotted against the various axes aren not drawn in any differentiated way: the viewer of the resulting plot has to be told which is which via an axes label, legend, colors, etc. Prior to version 1.25 of "feedgnuplot" the curves plotted on the y2 axis were drawn with a thicker line. This is no longer the case, but that behavior can be brought back by passing something like

     --y2 curveid --style curveid 'linewidth 3'
  • "--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). If a drawing style is not specified for this curve ("--curvestyle") or all curves ("--with", "--curvestyleall") then the default histogram style is set: filled boxes with borders. This is what the user generally wants. 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 domain values are not drawn in any way. Can be passed multiple times, or passed a comma- separated list

  • "--xticlabels"

    If given, the x-axis tic labels are not numerical, but are read from the data. This changes the interpretation of the input data: with "--domain", each line begins with "x label ....". Without "--domain", each line begins with "label ...". Clearly, the labels may not contain whitespace. This does not affect the tuple size. This makes sense only without "--3d". Please see the guide (<>) for usage examples.

  • "--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 frequency' gnuplot style. "--histstyle" can be used to select different "smooth" settings (see the gnuplot "help smooth" page for more info). Allowed values are 'frequency' (the default), 'fnormal' (available in very recent gnuplots), 'unique', 'cumulative' and 'cnormal'. 'fnormal' is a normalized histogram. '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 'frequency' histogram. 'cnormal' is like 'cumulative', but rescaled to end up at 1.0.

  • "--style curveID style"

    Additional styles per curve. With "--dataid", curveID is the ID. Otherwise, it's the index of the curve, starting at 0. curveID can be a comma-separated list of IDs to which the given style should apply. Use this option multiple times for multiple curves. "--styleall" does not apply to curves that have a "--style".

  • "--curvestyle curveID"

    Synonym for "--style"

  • "--styleall xxx"

    Additional styles for all curves that have no "--style". This is overridden by any applicable "--style". Exclusive with "--with".

  • "--curvestyleall xxx"

    Synonym for "--styleall"

  • "--with xxx"

    Same as "--styleall", but prefixed with "with". Thus

     --with boxes

    is equivalent to

     --styleall 'with boxes'

    Exclusive with "--styleall".

  • "--every curveID factor"

    Decimates the input. Instead of plotting every point in the given curve, plot one point per factor. This is useful to quickly process huge datasets. For instance, to plot 1% of the data, pass a factor of 100.

  • "--everyall factor"

    Decimates the input. This works exactly like "--every", except it applies to all the curves.

  • "--using curveID expression"

    Specifies a "using" expression to micromanage the plot. This is a powerful option that allows gnuplot to interpret the input data in arbitrary ways. A "using" expression tells gnuplot how to map the input columns of data to tuples expected by the plotting style. Please see the "'using' expressions" section above for more detail.

  • "--usingall expression"

    Global "using" expressions. This works exactly like "--using", except it applies to all the curves.

  • "--cmds xxx"

    Additional commands to pass on to gnuplot verbatim. These could contain extra global styles for instance. Can be passed multiple times.

  • "--extracmds xxx"

    Synonym for "--cmds xxx"

  • "--set xxx"

    Additional 'set' commands to pass on to gnuplot verbatim. "--set 'a b c'" will result in gnuplot seeing a "set a b c" command. Can be passed multiple times.

  • "--unset xxx"

    Additional 'unset' commands to pass on to gnuplot verbatim. "--unset 'a b c'" will result in gnuplot seeing a "unset a b c" command. Can be passed multiple times.

  • "--image filename"

    Overlays the data on top of a raster image given in "filename". This is passed through to gnuplot via "--equation", and is not interpreted by "feedgnuplot" other than checking for existence. Usually images have their origin at the top-left corner, while plots have it in the bottom-left corner instead. Thus if the y-axis extents are not specified ("--ymin", "--ymax", "--set 'yrange ...'") this option will also flip around the y axis to make the image appear properly. Since this option is just a passthrough to gnuplot, finer control can be achieved by passing in "--equation" and "--set yrange ..." directly.

  • "--equation xxx"

    Gnuplot can plot both data and symbolic equations. "feedgnuplot" generally plots data, but with this option can plot symbolic equations also. This is generally intended to augment data plots, since for equation-only plots you don't need "feedgnuplot". "--equation" can be passed multiple times for multiple equations. The given strings are passed to gnuplot directly without anything added or removed, so styling and such should be applied in the string. A basic example:

     seq 100 | awk '{print $1/10, $1/100}' |
       feedgnuplot --with 'lines lw 3' --domain --ymax 1
                   --equation 'sin(x)/x' --equation 'cos(x)/x with lines lw 4'

    Here I plot the incoming data (points along a line) with the given style (a line with thickness 3), and I plot two damped sinusoids on the same plot. The sinusoids are not affected by "feedgnuplot" styling, so their styles are set separately, as in this example. More complicated example:

     seq 360 | perl -nE '$th=$_/360 * 3.14*2; $c=cos($th); $s=sin($th); say "$c $s"' |
       feedgnuplot --domain --square
                   --set parametric --set "trange [0:2*3.14]" --equation "sin(t),cos(t)"

    Here the data I generate is points along the unit circle. I plot these as points, and I also plot a true circle as a parametric equation.

  • "--equation-below xxx"

    Synonym for "--equation". These are rendered below all the other data.

  • "--equation-above xxx"

    Like "--equation", but is rendered on top of all the other data.

  • "--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". If "--terminal" is given, "--hardcopy" sets only the output filename.

  • "--terminal xxx"

    String passed to 'set terminal'. No attempts are made to validate this. "--hardcopy" sets this to some sensible defaults if "--hardcopy" is set to a filename ending in ".png", ".pdf", ".ps", ".eps" or ".svg". If any other file type is desired, use both "--hardcopy" and "--terminal"

  • "--maxcurves N"

    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. The data is replotted before being purged. This is useful in streaming plots where the incoming data represents multiple iterations of the same process (repeated simulations of the same period in time, for instance).

  • "--rangesize curveID N"

    The options "--rangesizeall" and "--rangesize" set the number of values are needed to represent each point being plotted (see "Multi-value style support" above). These options are only needed if unknown styles are used, with "--styleall" or "--with" for instance.

    "--rangesize" is used to set how many values are needed to represent the range of a point for a particular curve. This overrides any defaults that may exist for this curve only.

    With "--dataid", curveID is the ID. Otherwise, it's the index of the curve, starting at 0. curveID can be a comma-separated list of IDs to which the given rangesize should apply.

  • "--tuplesize curveID N"

    Very similar to "--rangesize", but instead of specifying the range only, this specifies the whole tuple. For instance if we're plotting circles, the tuplesize is 3: "x,y,radius". In a 2D plot there's a 1-dimensional domain: "x", so the rangesize is 2: "y,radius". This dimensionality can be given either way.

  • "--rangesizeall N"

    Like "--rangesize", but applies to all the curves.

  • "--tuplesizeall N"

    Like "--tuplesize", but applies to all the curves.

  • "--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.

  • "--exit"

    This controls what happens when the input data is exhausted, or when some part of the "feedgnuplot" pipeline is killed. This option does different things depending on whether "--stream" is active, so read this closely.

    With interactive gnuplot terminals (qt, x11, wxt), the plot windows live in a separate process from the main "gnuplot" process. It is thus possible for the main "gnuplot" process to exit, while leaving the plot windows up (a caveat is that such decapitated windows aren't interactive). There are 3 possible states of the polotting pipeline:

The possibilities are:

Alive. Need to Ctrl-C to get back into the shell
Half-alive. Non-interactive prompt up, and the shell accepts new commands. Without "--stream" the goal is to show a plot, so a Dead state would not be useful.
"--stream", all data read in or the "feedgnuplot" process terminated
Alive. Need to Ctrl-C to get back into the shell. This means that when making live plots, the first Ctrl-C kills the data feeding process, but leaves the final plot up for inspection. A second Ctrl-C kills feedgnuplot as well.
Dead. No plot is shown, and the shell accepts new commands. With "--stream" the goal is to show a plot as the data comes in, which we have been doing. Now that we're done, we can clean up everything.

Note that one usually invokes "feedgnuplot" as a part of a shell pipeline:

 $ write_data | feedgnuplot

If the user terminates this pipeline with ^C, then all the processes in the pipeline receive SIGINT. This normally kills "feedgnuplot" and all its "gnuplot" children, and we let this happen unless "--stream" and no "--exit". If "--stream" and no "--exit", then we ignore the first ^C. The data feeder dies, and we behave as if the input data was exhausted. A second ^C kills us also.

  • "--geometry"

    Specifies the size, position of the plot window. This applies only to the "x11" gnuplot terminal, and has no effect otherwise. To control the window size for any other terminal, ask for the terminal explicitly, with the options specifying the size. For instance "--terminal 'qt size 1024,768'"

  • "--version"

    Print the version and exit


For a tutorial and a gallery please see the guide at <>

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 -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 2011-2021 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.

2022-03-04 perl v5.34.0