GIS file converter from .shp to gnuplot data file

shape2txt

#!/bin/bash

# Original code by Hagen Wierstorf (http://www.gnuplotting.org)
# http://www.gnuplotting.org/code/shape2txt
# Shamelessly modified by Sylvain Leroux for the worst

function usage() {
    echo "Usage:"
    echo "  shape2txt file.shp"
}

if [[ -z "$1"  || ! -f "$1" ]]
then
    usage >&2
    exit 1
fi

INFILE="$1"
CSVFILE="${INFILE%.*}.csv"
OUTFMT="${INFILE%.*}.%s.txt"

# convert shape files to csv
rm -f "$CSVFILE"
ogr2ogr -f CSV "$CSVFILE" "$INFILE" -lco GEOMETRY=AS_WKT

# Awk script to remove , between quotes
NORMALIZE=$(cat << 'EOT'
    BEGIN {
        FS=")+\"";
        OFS="";
    }

    NR==1 {
        $0=("SHAPE," $0);
    }

    NR > 1 {
        gsub(/,/,"|",$1);    # Replace embedded comas
        sub(/ \(+/,",",$1);  # Replace (( by a coma
        sub(/"/,"",$1);      # Remove unneeded quotes
    }
        
    {
        print
    }
EOT
)

# Core processing
PROCESS=$(cat << 'EOT'
    BEGIN {
        FS=",";
        OFS=" ";
    }

    NR==1 {
        # Parse header
        for(i = 0; i < NF; ++i)
            F[$i]=i;
    }

    $1=="POLYGON" {
        NP=1;
        P[1]=$2;
    }

    $1=="MULTIPOLYGON" {
        NP=split($2, P, /\)\)\|\(\(/);
    }

    NR > 1 {
        CCODE=$F["sov_a3"];
        CNAME=$F["sovereignt"];
        FILE=sprintf(OUTFMT, CCODE);
        FILES[FILE]=1; # Remember the file name
        for(i = 1; i <= NP; ++i) {
            sub(/\)\|\(.*/,"", P[i]); # XXX until I know how to deal with
                                      # holes in gnuplot, just discard them
                                      # see:
                                      # https://stackoverflow.com/questions/44921842
                                      # https://en.wikipedia.org/wiki/Enclave_and_exclave
            NV=split(P[i], V, /\|/);
            for(j = 1; j <= NV; ++j) {
                print V[j], CCODE, CNAME > FILE;
            }
            print "" > FILE;
        }
    }

    END {
        CMD = "cat ";
        for(key in FILES) {
           CMD=(CMD key " ");
        }

        system(CMD);
    }
EOT
)

awk "$NORMALIZE" "$CSVFILE" | \
    awk -v OUTFMT="$OUTFMT" "$PROCESS" > $(printf "${OUTFMT}" all)