Hi I am trying to find out what is the best location to save a cache file.
I have an Windows form application that updates user's data from the server using a custom tool.
I want to write the timestamp of the latest updates done on user's machine in the cache file.
Where is the best location for keeping this file:
1. in application directory (c:\program files..)
2. in a temp location e.g. Users profile folder or c:\windows\temp
3. in any location (e.g. c:\dataupdates) where user has full access to read/write to.
Not in the application directory. That much is clear. :) The application directory shouldn't even be writable by the program (or actually by the user account that runs the program). Although some applications still use this location, it has actually been deprecated since Windows 95, I believe, and it has become a real pain since the more rigid UAC applied in Windows Vista and 7.
So the most obvious options are:
The temp folder, which is for temporary files. Note however, that you will need to clean those files up. Temp folder is not automatically cleared by default, so adding new files all the time will consume increasingly much space on the hard drive. On the other hand, some users do clear their temp folders, or may have scripts installed that do that for them, so you cannot trust such files to remain. Also, this is not always C:\Temp of whatever. You'll have to ask Windows what the location is.
You can pick 'any' location. Note that you cannot write anywhere. You cannot even expect the C drive to exist. If you choose this, then you have to make it a configurable setting.
The %app data% directory, my personal favorite, which is a special directory for applications to store their data in. The advantage is, that you can ask Windows for this location, and you can make up a relative path based on that directory, so you don't really have to make it an application setting. For more info on how to get it, see also this question: C# getting the path of %AppData%
I would definitely choose the App Data path for this purpose.
Related
Our application collects data from an external device. This data primarily resides in memory, but is spooled to disk in temporary files until the user explicitly saves the data. This is to provide some recovery chance if the application crashes for some reason. Generally speaking, it works just fine.
Lately we've discovered, thanks to Windows becoming more forceful about automatic updates, that these files get deleted automatically during a reboot. So if Windows kills our application to automatically apply updates, the temporary files that would have allowed recovery are gone after the reboot.
I've tested the issue by killing the application on purpose and rebooting; indeed, the temporary files have vanished after the reboot.
The files are created using the Win32 API call GetTempFileName, along with GetTempPath. Everything I've read on the subject says these files are not automatically deleted ever, but they clearly are being deleted.
What can I do to stop this? Or should I just change where our safety data is stored?
What you are seeing is a new "Storage Sense" feature added in Windows 10.
How to Clear Temporary Files Automatically in Windows 10.
Windows 10 got the ability to clear temporary files automatically in a recent build. Starting with build 15014, a new option appeared in Settings.
When enabled, it can be set to clear items like temporary files, Recycle Bin, etc. You can turn them off individually.
Alternatively, another option would be to change your app to save its temporary files in a non-system temp folder that you control, rather than using GetTempPath(). And maybe also use something other than GetTempFileName() to create your temporary file names (like using date/times or guids instead), so Windows can't possibly track the temporary files you create. Then perhaps your files won't be deleted automatically by Storage Sense anymore.
The best solution IMO is not using the temporary folder which contains (as the name suggests) temporary files that can be deleted without any consequences.
Instead you should store them somewhere in the LocalAppdata folder.
Use SHGetFolderPath function to retrieve the actual location of the LocalAppData folder.
In LocalAppData create a folder whose name is that of your company and/or product name or some combination of both and store all your pseudo temporary files there.
Is it possible to append/remove a ressource file to a binary at execution time?
I have an application written with go, which saves/searches data from a database file, and i would like this database file to be embedded to the binary, and updated by the application itself.
This way the application would be self contained with its database.
Modifying the executable, this is generally a very bad idea.
Several issues pop right into my head, such as:
Does the current user have sufficient permissions?
Is the file locked during execution?
What about multiple running instances of the application?
Even if you manage to do just that, think of what anti-virus and firewall applications will say to it: most when they detect the change will flag the executable and/or contain it, or deny running it, or some may even delete it. Rightfully, as this is what many viruses do: modify existing executables.
Also virus scanner databases maintain reports where files (their contents) are identified based on the hash of their content. Modifying the executable will naturally change the file content hash, thus render the file unknown / suspicious to these databases.
As mentioned, just write / cache data in separate file(s), preferably in user's home folder or in the application folder (next to the executable, optionally in sub-folders). Or make the cache file / folder a changeable option (command line flags).
Technically, this is possible, but this is a bad idea. Your application could be run by users not having write permissions to your binary.
If you're talking about a portable app, your best option might be using a file in the same directory the binary is located, otherwise - use the user's home directory according to the conventions of the OS you're running on. You can use the os/user package to find the home directory.
I am creating a WIX installer project. During one managed customized action, I need to create a file (other than the deployed files specified in the components of WIX) in the installation folder, which by default is the Program Files folder. I am experiencing the "Access denied" problem in Windows 7. After some searching, I found out that people say it is not advisable to create files into Program Files folder. Instead, try to create files into for example AppData folder. For example, see this link:
C# Access denied to path in a Windows Application
But my question is, the generated file is crucial to our SW, so it must reside in the installation folder. Isn't it the target of SW installation, I mean, to create file in most of the cases Program Files folder? Does it mean the only files should be added into installation folder, during the installation, are the deployed files (basically the targets of XCopy)?
My file can't be made deploy-able in the WIX, i.e, it can't be made ready before the installation. So what's the proper way or best practice to handle such situation: a file must be generated during the installation, into the installation folder. It is not some log file that I can put somewhere else. I tried to create a Permission element in WIX for the INSTALLADIR, although it seems to be against the rule mentioned in the link, but it still failed. Thanks!
UPDATE:
Based one MichaelUrman's commen, some more information. The generated file is needed after the SW is installed and necessary during normal launch of the SW. And I think it needs to be modified during normal use after the installation. And as I mentioned my a comment to #caveman_dick answer, my CA is actually in commit phase, I don't know whether there is any difference between it and normal deferred CA
Set the custom action to Execute="deferred", that will run the command elevated and should give it the required permissions to create the file.
Since you need to update that file from the main application, and I'm assuming your application does not require elevated privileges, you have three options.
The first is the worst: without a manifest, your executable's attempts to write to the Program Files folder will typically result in it being redirected to the Virtual Store (see File Virtualization). It sounds like this isn't happening in your case, so you can't use it.
The second option is to modify the application to store this in an appropriate location such as the ProgramData folder, or Common Documents, or (if appropriate) a per-user location under LocalAppData. This is typically the best approach, but has the highest development costs.
Finally the third option is to create the file and change its permissions (or in some cases to change the permissions on the folder containing the file), allowing limited users to modify this file. See LockPermissions or MsiLockPermissionsEx for the Windows Installer way to approach this. Change the permissions on as few files or folders, as restricted as possible, to keep the system as safe as possible if you go with this option.
We are migrating our APP to Win7. The program generates log files to help us support and also saves a number of dictionary files and settings files that are useful for the user though the user will rarely if ever actually want to interact with the files outside of our application. They can though because they are csv files. I built the first run through with using the APPDATA\LOCAL\OURAPPLICATION folder as the destination. Now I am wondering if it should be PROGRAMDATA\OURAPPLICATION.
I actually think the first choice is better because it seems that everything I have scanned suggests that the PROGRAMDATA folder should be considered untouchable by the user but as I am not a programmer I am not sure.
I hope this is the right place to ask this question
The key point to consider is what the scope of the data is. If you are storing data that is associated with a specific user then you should use APPDATA and if you are storing data that is global to your program then you should use PROGRAMDATA.
Both APPDATA and PROGRAMDATA are hidden folders so the intent is for users not to be poking around in there (not that they couldn't if they wanted to).
I have an automatic update system that replaces my existing program files on reboot. (Suffice to say, it's a very complicated program with many drivers, services, and user level modules. There really is no other way. Trust me.)
The function MoveFileEx is used with MOVEFILE_DELAY_UNTIL_REBOOT to setup this file replacement. I'm finding that it works just fine, normally. However, if the source and target files are on different drives, the target is deleted but the source is not moved. The result is that when the user installs the software on a drive different from the system partition, an update deletes the product file rather than update them.
Now, I see in the documentation for MoveFileEx that MOVEFILE_COPY_ALLOWED should be used when moving a file from one volume to another. But it also says that flag cannot be used with MOVEFILE_DELAY_UNTIL_REBOOT.
Q: How can I move a file on reboot, overwriting an existing file, when the source and the target are not on the same volume?
Why don't you just copy the files to the drive where the user installed your program?
As far as I see there is no direct way to do what you want relying only on this function.
Finding writable location on the same drive might be a problem on Vista, but you mention you have services - if they run with LocalSystem privilleges have them write the new files.
One other simple update mechanism that I have used ( not working for drivers though) is to have dedicated update program - kill/end everything, let the update program do its work and start everything up again.