gog-backup

Download installers and extras for your GOG.com purchases

Author:	Evan Powers
Date:	2012-01-05
License:	GPLv3+
Manual section:	1

Synopsis

gog-backup [--version] [--help] <command> [<args>]

Description

gog-backup performs an unattended batch download of everything you've purchased from GOG.com, both game installers and available extras. When you make an additional purchase, just run gog-backup again to download only the new files necessary to make your backup complete.

Features

• Open source: The code is short and simple enough to be understood and/or customized without much effort.
• Cross platform: gog-backup is a pure Python program (as is its only dependency); it should run on any platform Python supports.
• Unattended batch download: Run one command to update your manifest, another to begin the download, and you can walk away.
• Resume partial downloads: Running gog-backup again after it aborts because of an error (or you terminate it yourself) will resume partial downloads where they left off. You can also resume partial downloads begun by other tools, like your web browser or the official GOG.com downloader.
• Verify and repair files: GOG.com publishes XML containing MD5 hashes for game installers and "chunks" thereof; gog-backup can compare files against this information. If one or more chunks of a file are corrupt, gog-backup will re-download only those chunks—not the entire file. For game extras, which lack XML metadata but are always .zip archives, gog-backup can detect corruption by validating the checksums internal to the archive format.
• Multithreaded downloads: gog-backup will perform as many downloads in parallel as you specify. You can choose whether all the threads should focus on one file until it is complete or should each download different files.
• Configurable directory hierarchy: gog-backup doesn't force you to organize your downloaded files in any particular way beyond putting all installers and extras for a particular game in the same directory.
• Covers and thumbnails: While this is disabled by default (because it's kinda pointless), gog-backup can download the box covers and thumbnails used to represent your games on the GOG.com website.

Installation

Obtain the gog-backup script directly from its GitHub page [1]. There are exactly two dependencies:

1. Python 2.6 or compatible, unless I'm wrong and it actually requires 2.7
2. html5lib [2], tested with 0.90

If you're a Python developer,

easy_install html5lib

may be the easiest way to obtain the second dependency; everyone else can just download the source archive from the aforementioned URL, extract it, and move the sub-folder src/html5lib into the directory containing gog-backup.

Note that gog-backup itself doesn't need to be placed anywhere in particular.

Basic Usage

While easy to use by virtue of having only a few sub-commands, gog-backup nevertheless has the flavor of a tool designed by a programmer; its response to most problems is to die and print a traceback. If you are not a programmer yourself, you'll need to bear with this.

For an overview of command line syntax and the supported sub-commands, run gog-backup --help.

• login <email> <password>

  Logs in to GOG.com using the supplied email and password, then saves the authentication cookie to disk for use during subsequent invocations. Neither the email nor password themselves are saved.

• manifest

  Parses your account pages on GOG.com to determine the complete list of games you own, then probes GOG.com's content servers for XML metadata and details like file size. (If enabled, it also downloads game covers and thumbnails.)

• list

  Prints a summary of the current manifest—a list of game unique names, the corresponding game titles, the total size and number of both setup files and extras for each, and the total disk space required for the complete backup.

• compare and update

  Verifies downloaded files by comparing them against available metadata from the manifest or internal checksums (in the case of .zip archives), then prints a report on what must be downloaded. Both commands update a cache of previous validation results; the difference is that compare re-validates everything, while update only considers files which have not been previously validated.

  compare is therefore useful for detecting corruption due to media wear or GOG.com posting an updated version of a file, but takes a long time if you own a lot of games.

• fetch

  Downloads any missing, incomplete, or corrupted files (after an implicit update). Failed HTTP requests are merely reported, not reattempted, so you should run fetch repeatedly until it stops downloading files (perhaps waiting an appropriate period between invocations if GOG.com is experiencing high load). By default, game files are placed in per-game sub-directories of the current working directory.

Therefore, the simplest command flow would be to first login, then download a manifest, then fetch one or more times.

If you have previously downloaded files using another tool, such as your web browser or the official GOG.com downloader, you needn't download them again; if you place them either directly in the backup directory or the sub-directory for the corresponding game, they'll be detected. Partial downloads can be resumed in this way as well.

Advanced Usage

While gog-backup doesn't require any configuration to work out of the box, there are a few things you can change if you feel the need to do so. Most are controlled by a group of global variables initialized near the top of the script; they include:

• BACKUPINTO: the directory into which all files, and gog-backup state, are placed; by default, the current working directory
• CONCURRENCY: the number of download threads to use
• BREADTHFIRST: whether the download threads should generally work on different files (True) or the same file (False)
• FETCHCOVERS: whether to download covers and thumbnails

By default, files for a particular game are downloaded into a sub-directory of BACKUPINTO named according to the unique name GOG.com uses for the game; this unique name is merely the last component of the URL for its description page. For example, beneath_a_steel_sky is the unique name of Beneath a Steel Sky, which is described at http://www.gog.com/en/gamecard/beneath_a_steel_sky.

You can override this default by creating a "path map", which is a text file mapping unique game names to the paths into which their files should be placed. The file must be named .gog.pathmap.txt and be located in BACKUPINTO; within the file, list on each line a unique name and the path into which that game's files should be placed, separated by one or more white-space characters. Paths can be relative to BACKUPINTO or absolute, and blank lines are not allowed. For example:

beneath_a_steel_sky      steelsky
lure_of_the_temptress    temptress
tyrian_2000              /opt/games/tyrian2k

The "path map" needn't be constructed in advance; you can adjust it at any time provided you move already downloaded files into the new location manually.

Bugs & Contributions

If you discover a bug, please submit it on GitHub, ideally including a patch that fixes the problem. If there's a feature you think is missing, feel free to implement it and send me a pull request. Known bugs and limitations include:

• Connection timeouts during manifest creation aren't handled, which makes large game collections problematic during peak hours.
• Files which are corrupt, truncated, and lack XML metadata cannot be distinguished from partial downloads. As a consequence, they'll be "resumed". Since only extras lack XML metadata, and extras are apparently always .zip files, the corruption will be detected after the download is "complete", but the post-"resume" data will need to be re-downloaded.
• Files lacking XML metadata which change in content but not in length will not be re-downloaded. For example, if GOG.com updates an extra in a way that does not affect the file's length, gog-backup will be unable to detect this.
• Passing the account password on the command line is a classic security flaw on multi-user machines—users can see each other's processes, and the command lines used to invoke those processes.

Alternatives

gog-backup is but one of several unofficial GOG.com downloaders; if it doesn't meet your needs, perhaps one of the others will. You can find a feature comparison at [3].

References

[1]	https://github.com/evanpowers/gog-backup

[2]	http://code.google.com/p/html5lib/

[3]	https://github.com/evanpowers/gog-backup/wiki/Comparison