#!/bin/bash

###
# Single pass tabulate.
#
# Turn grid-aligned tables into tab-separated values
#  using the first line as a template.
# Pre-existing tabs are preserved,
#  which is probably not good.
##
# TODO:
# - Optionally require more than one space for column separation.

shopt -s extglob

spitline(){
	declare -i prevtab=0
	for tabstop in ${tabstops[@]}
	do
		# Strip trailing spaces.
		field=${line:$prevtab:$((tabstop-prevtab))}
		field=${field%%*( )}
		printf '%s\t' "$field"
		prevtab=$tabstop
	done
	printf '%s\n' "${line:$prevtab}"
}

##
# First line:
##
# The tab stops are where stretches of empty space end.
IFS=$'\n'
read -r firstline
declare -i skip=1
for ((i=0;i<${#firstline};i++))
do
	case ${firstline:$i:1} in
		\ )
			skip=0
	;;	*)
			[[ $skip -eq 0 ]] && tabstops+=($i)
			skip=1
	esac
done
#echo >&2 ${tabstops[@]}
line=$firstline
spitline

##
# All other lines:
declare -i prevtab
while read -r line
do	spitline
done