split csv

split.sh

#!/usr/bin/env bash

# usage: ./split.sh <FILE> <LINES>

FILE_PATH="$1"
FILE_BASENAME="${FILE_PATH##*/}"
FILE_NAME="${FILE_BASENAME%%.*}"
FILE_EXTENSION="${FILE_BASENAME#*.}"
SPLIT_LINES=${$2:-500000}

gsplit --lines=$SPLIT_LINES --numeric-suffixes=1 --suffix-length=3 --additional-suffix=".$FILE_EXTENSION" "$FILE_PATH" "$FILE_NAME-"

for SPLIT in $FILE_NAME-*.$FILE_EXTENSION; do
    if [ -z "${SPLIT##$FILE_NAME-001.$FILE_EXTENSION}" ]; then
        continue
    fi

    head -n1 "$FILE_PATH" > temp_file
    cat "$SPLIT" >> temp_file
    mv -f temp_file "$SPLIT"
done