#!/bin/bash
this="${0##*/}"
USAGE="\
usage:  $this [<awk_args>] <field_no>
    Ex: getent passwd | grep andy | $this -F: 5
    Ex: echo \"A B\" | $this 2
"
err(){ echo -e "$USAGE" >&2; exit 1; }

[[ $# -eq 0 ]] && err
# bail if the *last* argument isn't a number (source:
# http://stackoverflow.com/a/808740)
last=${@:(-1)}
if ! [ $last -eq $last ] &>/dev/null; then
    echo "_awk! Last argument (awk field) must be numeric." >&2
    err
fi

if [ $# -gt 1 ]; then
    # Source:
    # http://www.cyberciti.biz/faq/linux-unix-bsd-apple-osx-bash-get-last-argument/
    rest=${@:1:$(( $# - 1 ))}
else
    rest='' # just to be sure
fi
awk $rest "{ print  \$$last }"