#!/bin/sh
for archive in "$@"; do
    # count files in root dir
    rootfiles=$(7z l -slt "${archive}" | grep -c 'Path = [^/]*$')

    # add -o switch, if more than one file in root
    # checks for >2, because path of the zip file itself is listed too
    if [ $rootfiles -gt 2 ]; then
        filename=${archive##*/}
        rootname=${filename%.*}
        opt="-o${rootname}"
    fi

    #unpack
    7z x "${opt}" "${archive}"
done