[template on shell script with file-ext validation]

02_strip_header.sh

#!/bin/sh

input_ext=".csv"

# simple check on input file extension
if [ "${1%$input_ext}" != $1 ]
then

    header_file="${1%$input_ext}.header"
    stript_file="${1%$input_ext}.noheader"

    echo '... remove header line in' $1

    # a simple check on the first words of the first line
    first_line_start_with=$(head -n 1 $1 | cut -c-5)
    if [ $first_line_start_with = '"NPI"' ]
    then
        head -n 1 $1 > $header_file
        sed '1d' $1 > $stript_file
    else
        echo '...     (no header found in' $1 ')'
        cp $1 $stript_file
    fi

    echo

else

    echo "!!! please provide a $input_ext file"
    echo "!!! exiting ..."
    echo
    exit 1

fi