unzipdir.sh v3

#! /bin/bash
#unzipdir
#Version 3
#safely extracts the zip equivalent of tarbombs
#v2 works on zipfiles with extensions other than .zip (like .xpi and some .cbr files)
#By Wyatt Ward, but with some things snatched from stack exchange answers
#Requires info-zip

# version 3 allows you to immediately 'cd' into the created dir with this
# syntax:
#   cd $(unzipdir zipfile.zip)
# or:
#   cd `unzipdir zipfile.zip`
# (depending on your shell.)
#
export INFILENAME=`echo "$@" | awk -F/ '$0=$NF'` #Looking back, i forget exactly what this does, but I think it cuts out a path.
export INFILEBASENAME=$(basename "$INFILENAME")
export INFILEEXTENSION="${INFILEBASENAME##*.}" #not sure how it works. thanks stack exchange

#original v1 line:
#export OUTPUTDIR=`echo "$INFILENAME" | sed 's/.zip//g'`
#new v2 line:
export OUTPUTDIR=`echo "$INFILENAME" | sed "s/.$INFILEEXTENSION//g"`

# echo "OUTPUTDIR is"
# echo "$OUTPUTDIR"
export STARTINGDIR="$PWD"
if [ -f "$1" ]
then
#        echo "Found file."
        mkdir "$OUTPUTDIR"
        cd "$OUTPUTDIR"
        if [ `echo "$1" | grep [/]` ]
        then
#leading slash present, no need to find actual paths
#                unzip "$1"
# quiet unzip
                unzip -qq "$1"
        else
#no slash present, be paranoid and do it the harder way
#                unzip "$STARTINGDIR/$1"
# quiet unzip
                unzip -qq "$STARTINGDIR/$1"
        fi
# print destination directory name so we can cd into it
        echo "$OUTPUTDIR"
else
# print to stderr
        echo "$1 not found." >&2
fi