How do I re-zip/compress an expanded IDML file - adobe-indesign

Question

I have an IDML file that I unzipped. I now want to compress the expanded folder back into an IDML file. I have access to a Mac or Linux machine.
What are the ways I can do this?
Zipping the file using zip (command line) or with Keka, BetterZip or Archive Utility don't work. InDesign issues the error:
Cannot open the file. Adobe InDesign may not support the file format, a plug-in that supports the file format may be missing, or the file may be open in another application.

Answer 1

The problem with regular zip is that the zip archive contains a “mimetype” file that shouldn’t be compressed if you want InDesign to identify the newly-created IDML. So the way you have to re-zip the file (and the way the ePub scripts work) is like this:
They first create a zip archive which contains only the mimetype file, uncompressed. zip -X0 'myfile.idml' mimetype
Then they add the rest of the files/folders into the zip archive, this time with full compression. zip -rDX9 "myfile.idml" * -x "*.DS_Store" -x mimetype
In shell script terms, the ePub scripts do this (assuming the current directory is the one containing all the IDML contents):
zip -X0 'myfile.idml' mimetype # create the zip archive 'myfile.idml', containing only the 'mimetype' file with no compression
zip -rDX9 "myfile.idml" * -x "*.DS_Store" -x mimetype # add everything else to the ‘myfile.idml’ archive, EXCEPT .DS_Store files and the ‘mimetype’ file (which is already there from the previous step)
To save you time reading the zip man page, here’s what all these options mean:
-X = “no extra” — do not save extra file attributes like user/group ID for each file
-0 = “compression level zero” — no compression
-r = “recurse paths” — go through everything in the directory, including nested subfolders
-D = “no directory entries” — don’t put special stuff in the zip archive for directories
-9 = “compression level 9 (optimal)”
-x = “exclude these files”
Follow this voodoo, and you should be able to create legal IDML files.
Source: http://indesignsecrets.com/topic/how-do-i-re-zipcompress-an-expanded-idml-file
A big thanks to Chuck Weger and David Blatner at http://indesignsecrets.com

Answer 2

From within InDesign
use this jsx script to expand an IDML
//DESCRIPTION: Expands an IDML file into folder format
ExpandIDML();
function ExpandIDML(){
var fromIDMLFile = File.openDialog("Please Select The IDML File to unpackage");
if(!fromIDMLFile){return}
var fullName = fromIDMLFile.fullName;
fullName = fullName.replace(/\.idml/,"");
var toFolder = new Folder(fullName);
app.unpackageUCF(fromIDMLFile,toFolder);
}
And that one to produce an IDML package:
//DESCRIPTION:Produces an IDML package from the contents of a directory:
CreateIDML();
function CreateIDML(){
var fromFolder = Folder.selectDialog("Please Select The Folder to package as IDML");
if(!fromFolder){return}
var fullName = fromFolder.fullName;
// var name = fromFolder.name;
// var path = fromFolder.path;
var toIDMLFile = new File(fullName+".idml");
app.packageUCF(fromFolder,toIDMLFile);
}