Splits large files into smaller files of 1000 lines, keeping the header on each small file

gist_split_large_files_with_header.bash

%%bash
# echo $filepath

in_file=$in_filepath

DIR=$(dirname "$in_filepath")
filename=$(basename -- "$in_filepath")

extension="${filename##*.}"
#filename="${filepath##*/}" # This one will keep the extension
filename="${filename%.*}" # This will not have the extension
target=$DIR/$filename  # removing the extension

echo $target


awk '{if (NR!=1) {print}}' $in_file | split -d -a 5 -l 1000 - $target"__" # Get all lines except the first, split into 1000 line chunks
for file in $target"__"*
do
    
    tmp_file=$(mktemp $in_file.XXXXXX) # Create a safer temp file
    head -n 1 $in_file | cat - $file > $tmp_file # Get header from main file, cat that header with split file contents to temp file
    mv -f $tmp_file $file # Overwrite non-header containing file with header-containing file
    mv -f $file $file.$extension  # adding the extension
done