ftdmp-extract-table-columns

#!/bin/bash

function print_help_and_exit
{
cat >&2 << 'EOF'

'ftdmp-extract-table-columns' extracts only specified table columns

Options:
    space-separated table

Standard output:
    space-separated table
    
Example:

    ftdmp-extract-table-columns colname1 colname2 colname3

EOF
exit 1
}

if [ -z "$1" ]
then
	print_help_and_exit
fi

readonly TMPLDIR=$(mktemp -d)
trap "rm -r $TMPLDIR" EXIT

while [[ $# > 0 ]]
do
	COLNAME="$1"
	shift
	
	if [ -z "$COLNAME" ]
	then
		echo >&2 "Error: empty column name in arguments"
		exit 1
	fi
	
	echo "$COLNAME" >> "$TMPLDIR/input_list"
done

INCOUNT="$(cat "$TMPLDIR/input_list" | sort | uniq | wc -l)"

if [ "$INCOUNT" -lt "1" ]
then
	echo >&2 "Error: no input column names provided"
	exit 1
fi

cat > "$TMPLDIR/input_table"

head -1 "$TMPLDIR/input_table" | sed 's/\s\+/\n/g' | egrep . > "$TMPLDIR/input_table_columns"

MATCHEDCOUNT="$(cat "$TMPLDIR/input_table_columns" | awk '{print ";" $1 ";"}' | grep -f <(cat "$TMPLDIR/input_list" | awk '{print ";" $1 ";"}') | sort | uniq | wc -l)"

if [ "$INCOUNT" != "$MATCHEDCOUNT" ]
then
	echo >&2 "Error: provided column names do not match the input table column names"
	exit 1
fi

{
echo 'NR==1 {for(i=1;i<=NF;i++){f[$i]=i}}'
echo '{print'
cat "$TMPLDIR/input_list" | sed 's/^/\$(f[\"/' | sed 's/$/\"]),/'
echo "}"
} \
| tr '\n' ' ' \
| sed 's/,\s*}/}/' \
| sed 's/$/\n/' \
> "$TMPLDIR/awk_script"

cat "$TMPLDIR/input_table" | awk -f "$TMPLDIR/awk_script"