#!/bin/bash

    # This script copies the pgplot files that correspond to zone plots
    # (i.e., every fifth plot) into a folder called zone, and then creates
    # an animated gif of those plots called zone.gif. A temporary file
    # zone_files is created and removed.

    # the corresponding pgplot files are posted as pgplot.tar

    # first check if the zone directory exists
    if [ ! -d zone ]
    then
        mkdir zone # it doesn't exist, create it
    else
        # it exists, remove it, then recreate it
        rm -r zone # you will need to add -f if rm has been aliased to
                   # rm -i to avoid being asked about every file
        mkdir zone
    fi
    n=$(ls pglot* | wc -l) # count how many pgplot files we have
    > zone_files # create the zone_files file and make sure it's empty
    for (( i=5; i < n; i+=5 ))
    do
        cp "pgplot_$i.png" "zone/plot_$i.png"
        echo "zone/plot_$i.png" >> zone_files # append the current plot
                                              # filename to zone_files
    done

    convert -delay 10 @zone_files zone.gif # create the gif