split csv file into several files by a given number of items, head row is preserved

splitcsv.sh

#!/bin/sh

tail -n +2 activity.csv | split -l 8000 - split_
for file in split_*
do
    head -n 1 activity.csv > tmp_file
    cat $file >> tmp_file
    mv -f tmp_file "$file.csv"
    rm $file 
done