Как сконвертировать обатно в .wln?

#!/bin/bash

# Function to convert Excel serial date to Unix timestamp in seconds
serial_to_unix() {
    serial_date="$1"
    # Excel date starts from 1-Jan-1900, while Unix date starts from 1-Jan-1970
    excel_epoch=25569  # Number of days between 1-Jan-1900 and 1-Jan-1970
    seconds_per_day=86400

    # Convert the serial date to Unix timestamp and ensure integer value
    unix_time=$(echo "($serial_date - $excel_epoch) * $seconds_per_day / 1" | bc)
    echo "$unix_time"
}

# Function to convert Unix timestamp to nanoseconds (WLNTMNS)
unix_to_nanoseconds() {
    unix_time="$1"
    # Convert Unix timestamp to nanoseconds
    nanoseconds=$(echo "$unix_time * 1000000000" | bc)
    echo "$nanoseconds"
}

# Prompt user for the .plt file name
read -p "Enter the .plt file name (including extension): " plt_file

# Check if file exists
if [[ ! -f "$plt_file" ]]; then
    echo "File not found!"
    exit 1
fi

# Create output file name with .wln extension
output_file="${plt_file%.*}.wln"

# Ensure the output file is empty or created
: > "$output_file"

# Reading each line of the plt file and saving output to the .wln file
while IFS=',' read -r lat lon third altitude serial_date; do
    # Strip any leading/trailing whitespace and remove carriage return
    lat=$(echo "$lat" | tr -d '\r' | xargs)
    lon=$(echo "$lon" | tr -d '\r' | xargs)
    altitude=$(echo "$altitude" | tr -d '\r' | xargs)
    serial_date=$(echo "$serial_date" | tr -d '\r' | xargs)

    # Debugging output
    echo "Processing line: lat=$lat, lon=$lon, altitude=$altitude, serial_date=$serial_date"

    # Check if the line contains valid numeric fields for lat, lon, altitude, and serial_date
    if [[ "$lat" =~ ^-?[0-9]+(\.[0-9]+)?$ ]] && [[ "$lon" =~ ^-?[0-9]+(\.[0-9]+)?$ ]] && [[ "$altitude" =~ ^-?[0-9]+(\.[0-9]+)?$ ]] && [[ "$serial_date" =~ ^-?[0-9]+(\.[0-9]+)?$ ]]; then
        # Convert serial date to Unix timestamp
        unix_time=$(serial_to_unix "$serial_date")

        # Ensure the Unix time is not empty and is an integer
        if [[ -z "$unix_time" ]] || ! [[ "$unix_time" =~ ^[0-9]+$ ]]; then
            echo "Error converting serial date $serial_date to Unix timestamp."
            continue
        fi

        # Convert Unix timestamp to nanoseconds (WLNTMNS)
        nanoseconds=$(unix_to_nanoseconds "$unix_time")

        # Format the line and append to the output file
        echo "REG;$unix_time;$lon;$lat;0;0;ALT:$altitude;SATS:5;;WLNTMNS:$nanoseconds;;" >> "$output_file"
    else
        echo "Skipping line: lat=$lat, lon=$lon, altitude=$altitude, serial_date=$serial_date"
    fi
done < "$plt_file"

echo "Conversion completed. Output saved to $output_file."