gistfile1.sh

#!/bin/bash
# decomp - decompress arbitrary archives by extension
# author: Tim Hammerquist <penryu@gmail.com>

UNZIP=`which unzip`
TAR=`which tar`

extract_zip="$UNZIP"
extract_tgz="$TAR zxf"
extract_tbz="$TAR jxf"
extract_tar="$TAR xf"

archive=$1

case "$archive" in
    *.zip)               $extract_zip $archive ;;
    *.tar.gz | *.tgz )   $extract_tgz $archive ;;
    *.tar.bz2 | *.tbz2 ) $extract_tbz $archive ;;
    *.tar)               $extract_tar $archive ;;
    *)
        if [[ "$archive" =~ \.((tar\.)?([^.]+))$ ]]; then
            ext=${BASH_REMATCH[1]}
            echo "Can't determine archive type for extension '$ext'."
        else
            echo "Can't determine file type for '$archive'."
        fi
        exit 1
esac

This was just an exercise for a lab at school.