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Fusion CLI

Applies to

Integrate directly using the command line interface.

If there isn't a native library, or command line bindings for your language yet, you can directly integrate Velopack using the command line.

There are two binaries needed.


Vfusion.exe / VfusionMac / VFusionNix
Provides support for getting current version, checking for updates, downloading updates etc.


At this time, the fusion binary is not automatically distributed, and you need to copy this into your compiler output directory. You can download a recent build artifact and make sure it's copied to your output dir during builds.


> Vfusion.exe check --url

These are the possible outputs:

  • No updates are available: empty stdout and exitCode == 0.
  • Unrecoverable error: empty stdout and exitCode != 0. A log file will be created.
  • Update is availble: stdout contains json object and exitCode == 0.

When an update is available, you'll receive an UpdateInfo object via stdout:

"isDowngrade": false,
"targetFullRelease": {
"packageId": "YourPackageId",
"version": "2.0.1",
"type": "Full",
"fileName": "YourPackageId-2.0.1-full.nupkg",
"sha1": "331a4f44a6a875b2ce139ae0c9ce5bb5e1ec0d97",
"size": 90654,
"notesMarkdown": "# Release v2.0.1 \n Your message here",
"notesHtml": "<h1>Release v2.0.1</h2><br/>Your message here"

The next step is to download an update to disk, using the fileName property from the previous command:

> Vfusion.exe download \
--url \
--name YourPackageId-2.0.1-full.nupkg

During this command, fusion will output the current download progress to stdout. For example:


You can parse each line of stdout (split by \n) and show progress to your users.

If exitCode == 0 the command was successful.

To get the final path to the downloaded asset, you can combine the result of Vfusion.exe get-packages and fileName.

To install the update, please see the next section.


There are other commands (eg. get-version) which may be useful, explore them with Vfusion.exe -h


Update.exe / UpdateMac / UpdateNix
Provides support for installing downloaded updates, prompting for elevation (if required), bootstrapping dependencies, and so forth.


This binary is automatically copied into your package when building vpk, you just need to locate it relative to your main executable.

You will use the update apply command to install a downloaded update.


> Update.exe apply --restart

Running the above command will immediately close your program, install the update, and restart your app on the new version.


If called with no arguments, Update will apply the newest downloaded release, as long as it's newer than the currently installed release. If you would like to install an older release, you need to specify the --package parameter.

All of the available apply options are below:

update apply:
Applies a staged / prepared update, installing prerequisite runtimes if necessary
-r, --restart Restart the application after the update
-w, --wait Wait for the parent process to terminate before applying the update
--waitPid <PID> Wait for the specified process to terminate before applying the update
-p, --package <FILE> Update package to apply
-h, --help Print help
[EXE_ARGS]... Arguments to pass to the restarted executable. Must be preceeded by '--'.


Since errors are not printed on stdout, it is important to know where to locate log files to diagnose errors.


Updater will log to it's own directory, and Fusion will log to the folder one above itself. In a typical installation, this will result in both the Fusion logs and Updater log being merged into one log file.

Linux and MacOS

On UNIX-like operating systems, the logs for these binaries always go to /tmp/velopack.log.