fields

#!/usr/bin/env bash

delimiter=' '
flags=("Fields: a small script that just prints out fields from either a file input or stdin" "    -dl []: delimiter character default ' '")

if [ $# == 0 ]; then
  echo "Pass the number of the field"
  exit 1
fi

init="{print"
file_name=""

is_digit() {
  [[ "$1" =~ ^[0-9]+$ ]]
}

i=1
while [ $i -le $# ]; do
  flag="${!i}"
  if is_digit "$flag"; then
    init+=" \$$flag"
    if ! [ $i = $# ]; then
      init+=", "
    fi
  elif [ "$flag" = "-dl" ]; then
    i=$((i + 1))
    delimiter="${!i}"
  elif [ "$flag" = "-h" ]; then
    for flag in "${flags[@]}"; do
      echo "$flag"
    done
    exit 0
  else
    file_name="${!i}"
  fi

  i=$((i + 1))
done

init+="}"

awk "$init" FS="$delimiter" OFS=' ' "$file_name"