#!/bin/bash
# Copyright (C) 2014 Ian Kelling
# This program is under GPL v. 3 or later, see <http://www.gnu.org/licenses/>

teeu() {
    local help="Usage: appendu [-h|--help] FILE [LINE]

Tee unique. Append each LINE or if none, each stdin line to FILE if it does not exist in FILE.

  [-h|--help]  display this message"
    
    if [[ $1 == --help || $1 == -h ]]; then
        echo "$help"
        return
    fi
    
    if (( ${#@} == 0 )) ; then
        echo "teeu error: need 1 or more arguments"
        echo "$help"
        return 1
    fi
    local MAPFILE
    (( ${#@} >= 2 )) && MAPFILE="${@:2}" || mapfile -t
    for line in "${$MAPFILE[@]}"; do
        grep -xFq "$line" "$1" &>/dev/null || tee -a "$1" <<<"$line"
    done
    return 0
}
teeu "$@"