Split csv file into multiple csv files usind sed, retaining header

split-csv.sh

#!/bin/bash

fileName=$1
maxLines=$2

echo "File name: $fileName"
echo "Max Lines: $maxLines"

getGotalLinesCommand="cat $fileName | wc -l"
totalLines="$(eval $getGotalLinesCommand)"
let totalLines--
echo "Number of Rows: $totalLines"

if [ $totalLines -lt 2 ] || [ $maxLines -lt 1 ]
then
    echo "Exiting"
    exit 1
fi

let totalFiles=totalLines/maxLines
if [ $(expr $totalLines % $maxLines) -gt 0 ]
then
    let totalFiles++
fi
echo "Total files: $totalFiles"

extractHeaderCommand="sed -n '1,1p;2q' $fileName"
header="$(eval $extractHeaderCommand)"

echo "Header: $header"

let startLine=2
let "endLine = $startLine + $maxLines - 2"

for ((i=1; i <= $totalFiles; i++))
do
    newFileName=${fileName%.csv}-$i.csv

    echo $header > $newFileName    
    sed -n "$startLine,${endLine}p" $fileName >> $newFileName

    echo "$newFileName Start: $startLine | End: $endLine | Total rows written: $( expr $endLine - $startLine + 1 )"

    let "startLine = $startLine + $maxLines - 1"
    let "endLine = $startLine + $maxLines - 2"
    let "quitLine = $endLine + 1"
    
    if [ $i -eq $( expr $totalFiles - 1 ) ]
    then
        let "endLine = $totalLines"
    fi
done