How to close Gnu process?

Question

I'm trying to make a script using Perl and the Chart::Gnuplot module for Linux to represent a series of data. It is something like this:

use strict;
use warnings;

use Chart::Gnuplot;

die "Linux check" if ( $^O ne 'linux' );

my $chart = Chart::Gnuplot->new(
    terminal => 'x11',
    title    => {
        text => "GRAPH",
        font => "Arial, 20"
    },
    xlabel => {
        text  => "X AXIS",
        font   => "arial, 20",
        offset =>"0,-1"
    },
    ylabel => {
        text   => "Y AXIS",
        font   => "arial, 20",
        offset =>"-6,0"
    },
);

my $dataSet = Chart::Gnuplot::DataSet->new(
    xdata => \@x_data,
    ydata => \@y_data,
    style => "points",
);

$chart->plot2d($dataSet);

exit;

When I run this from Eclipse, the script works OK and the graph shows correctly, but the process won't terminate (closing the Gnuplot window won't work). Something similar happens when I run it at the terminal.

The problematic line is $chart->plot2d($dataSet) without which it can terminate correctly. What could I do to end it right after closing the window?

Answer 1

Chart::Gnuplot runs gnuplot with the same stdin and other file descriptors open. After drawing the picture, gnuplot reads stdin waiting for more commands.

One solution is to simply redirect stdin to /dev/null in your perl program before doing the plot. This will also make the image immediately appear and disappear, so you should also add the persist option. Here are the 2 lines to change:

my $chart = Chart::Gnuplot->new(
    terminal => 'x11 persist',
...
open(STDIN, "<", "/dev/null") or die "Can't open /dev/null: $!";
$chart->plot2d($dataSet);