CSV Splitter. Use as ./csv-splitter.sh [your_csv_filename] [number_of_lines_to_split_into]

csv-splitter.sh

#!/bin/bash
FILENAME=$1
FILESIZE=$(stat -c%s "$FILENAME")
FILELINES=$(wc -l < $FILENAME)
SPLITRATIO=$(($FILESIZE / 9500000))
[ -z "$2" ] && LINES=$(($FILELINES / $SPLITRATIO)) || LINES=$2

TRIM="${FILENAME:0:${#FILENAME}-4}"
HDR=$(head -1 $FILENAME)
split -l $LINES $FILENAME xyz
n=1
for f in xyz*
do
        echo $HDR > $TRIM"_"${n}.csv
        cat $f >> $TRIM"_"${n}.csv
        rm $f
        ((n++))
done

Update 2018-09-05: the Bash script now tries to split CSV files into smaller CSV files just under 10MB if a line number is not passed as a variable.