xlsx, pptx, docx 같은 문서 압축파일과 zip 파일을 구분하는 방법을 알고 싶습니다.

#------------------------------------------------------------------------------
# $File: msooxml,v 1.3 2013/09/12 16:08:07 christos Exp $
# msooxml:  file(1) magic for Microsoft Office XML
# From: Ralf Brown <ralf.brown@gmail.com>
 
# .docx, .pptx, and .xlsx are XML plus other files inside a ZIP
#   archive.  The first member file is normally "[Content_Types].xml".
#   but some libreoffice generated files put this later. Perhaps skip
#   the "[Content_Types].xml" test?
# Since MSOOXML doesn't have anything like the uncompressed "mimetype"
#   file of ePub or OpenDocument, we'll have to scan for a filename
#   which can distinguish between the three types
 
# start by checking for ZIP local file header signature
0               string          PK\003\004
!:strength +10
# make sure the first file is correct
>0x1E           string          [Content_Types].xml
>>0             use             msooxml
>0xE84          string          [Content_Types].xml
>>0             use             msooxml
 
0               name            msooxml
# skip to the second local file header
# since some documents include a 520-byte extra field following the file
# header, we need to scan for the next header
>(18.l+49)      search/2000     PK\003\004
# now skip to the *third* local file header; again, we need to scan due to a
# 520-byte extra field following the file header
>>&26           search/1000     PK\003\004
# and check the subdirectory name to determine which type of OOXML
# file we have.  Correct the mimetype with the registered ones:
# <a href="http://technet.microsoft.com/en-us/library/cc179224.aspx
>>>&26" rel="nofollow">http://technet.microsoft.com/en-us/library/cc179224.aspx
>>>&26</a>          string          word/           Microsoft Word 2007+
!:mime application/vnd.openxmlformats-officedocument.wordprocessingml.document
>>>&26          string          ppt/            Microsoft PowerPoint 2007+
!:mime application/vnd.openxmlformats-officedocument.presentationml.presentation
>>>&26          string          xl/             Microsoft Excel 2007+
!:mime application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
>>>&26          default         x               Microsoft OOXML