CODEWITHSUNDEEP
pythonbashdmg
user7450368
user7450368

Reputation:

Automatically get contents of DMG file

I have a Python program that applies or removes multiple layers of encryption from a file. In this case, I have to open a DMG to access the ZIP file inside. I have used hidutil to make the DMG, but I am stuck on how to open it and access the file -- any method that I've seen relies on mounting, accessing the mount point and unmounting, which I cannot do without intelligently searching for where it was mounted to.

How do I do this? It doesn't have to be in Python, a Bash solution is fine.

Upvotes: 1

Views: 5263

Answers (3)

Cole Tierney
Cole Tierney

Reputation: 10314

Here's a bash version which parses the hdiutil output to extract the mount point for zip file access and the dev entry for detaching afterwards:

#!/bin/bash

dmg_path="$1"

# use process redirection to capture the mount point and dev entry
IFS=$'\n' read -rd '\n' mount_point dev_entry < <(
    # mount the diskimage; leave out -readonly if making changes to the filesystem
    hdiutil attach -readonly -plist "$dmg_path" | \

    # convert output plist to json
    plutil -convert json - -o - | \

    # extract mount point and dev entry
    jq -r '
        .[] | .[] |
        select(."volume-kind" == "hfs") |
        ."mount-point" + "\n" + ."dev-entry"
    '
)

# work with the zip file
ls "$mount_point/*.zip"

# unmount the disk image
hdiutil detach "$dev_entry"

Upvotes: 1

Mark Setchell
Mark Setchell

Reputation: 207475

You can list and extract the contents of a DMG file with 7zip - the website is here.

On macOS, 7zip can be installed with homebrew using:

brew install p7zip

Then if you have a DMG file, you can list the contents with:

7z l SomeDisk.dmg

Sample Output 

7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=utf8,Utf16=on,HugeFiles=on,64 bits,8 CPUs x64)

...
...

Modified = 2018-01-14 13:28:17

   Date      Time    Attr         Size   Compressed  Name
------------------- ----- ------------ ------------  ------------------------
2018-01-14 13:28:16 D....                            MyFunkyDMG
2018-01-14 13:28:16 D....                            MyFunkyDMG/.HFS+ Private Directory Data
2018-01-14 13:28:17 .....       524288       524288  MyFunkyDMG/.journal
2018-01-14 13:28:16 .....         4096         4096  MyFunkyDMG/.journal_info_block
2017-08-27 13:50:45 .....          255         4096  MyFunkyDMG/client.py
2017-08-27 13:49:22 .....          356         4096  MyFunkyDMG/server.py
2018-01-14 13:28:16 D....                            MyFunkyDMG/[HFS+ Private Data]
------------------- ----- ------------ ------------  ------------------------
2018-01-14 13:28:17             528995       536576  4 files, 3 folders

Then you can extract, say to a new directory called FRED with:

7z x -oFRED SomeDisk.dmg

A benefit of using 7zip is that the disk doesn't suddenly flash up on your Desktop as being mounted.

Upvotes: 5

jcragun
jcragun

Reputation: 2198

Based on this answer you can use hdiutil info -plist to get the mount point for a dmg through Python. That way you can mount, find mount point, list contents, and unmount intelligently.

Upvotes: 0

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