I am working on File Management System exactly like Dropbox in Cocoa.
My problem is when i edit any text file at that time NSFileSystemFileNumber is changed.
I want an unique NSFileSystemFileNumber even if that edited file is moved from the particular folder.
In short, I just want to know how to fetch that moved file's old or original path from the database.
Any alternate way to solve out this problem?
Thanks in Adv..!!
It depends on how the editor save functionality is implemented. Each editor will have different functionality and it sounds like the one you are using does the following:
Delete existing file.
Create new file.
Write file data.
Hence you get a new inode each time. Others might:
Truncate existing file.
Write file data.
which would result in the same inode each time.
There is nothing you can about this so you will need to track file changes using the name or something, not the inode.
Related
Sorry if this seems stupid but I wonder if it's possible to add a database entry after an ftp upload.
To be more clear, thanks to winSCP I have several folders sending everything I put in there automatically to my server.
However, I would like to create a mysql entry for each uploaded files and once again, automatically. Is it possible to do that? How?
To gives the full details of what I need to do, you can read the following.
I have several folders with pictures and each folders are uploaded automatically.
Each of those folders belong to one user and the goal is to give them an account and allow them to see and download those files through a web interface. Since one account = one folder, that's kinda easy.
And I think a simple .htaccess can simply secure things so one user can only see and download the file in his own repository, no?
However if I want them to be able to see what's new (=something they didn't download or simply mark as read) I think I need a table to manage those files.
Something like id | file (string) | read (bool).
If you think this way to proceed is bad, they I'm open to change how to do things, but to be clear uploading the file need to work this way. Not using any kind of formulary.
Thanks for reading that, sorry for my english.
Your problem contains three steps:
Folders/Files been automatically uploaded to your server directory, as you say, this been efficiently handled by winSCP.
You need to update your database with all the files and folders present in your server directory.
You need to update whether or not it is been read/downloaded by the user.
Since your first step is in place, we don't need anything there. For second step, you should write a script and schedule that script to run at a fixed time interval using CRON (if using LINUX or UNIX, or WINDOWS). The script would be responsible to create a list of file(s) present in the directory, and simply insert the file(s) information that are not present in your database.
EDIT:
This edit is to describe how your script file should work. As I explained, the cron jobs would simply help you run your script file in fixed set of interval (which can be every minute, or every hour, or every day, and so on). Lets say your database table has following columns:
fileid (varchar[20])
filepath (varchar[20])
status (boolean)
Your script file should do following things:
Create a list of existing filepaths in your server directory
Run a select query, create a list of existing filepaths from database table.
Compare list1 with list2, and find the ones that doesn't exist in list2 (This would give you a list of filepath that needs to be inserted into table)
Just insert the list of file paths you got above, and set there status to be false (which means the file is not read/downloaded yet)
NOTE: Please keep in mind that I am not advising right now that how your database table should look like. It can be what you have proposed or can even differ depending on your will or requirements.
For the third step, simply keep the status of your file to be unread when creating entries in your table from the second step, and then when user click on the file link in your application whether to view or download it, send a POST request to your server updating the file status to be marked as read.
Let me know if this helps!
I'm trying to do the following:
Read a file's attributes
If the attributes match a certain condition,
delete the file
Right now I'm using NSFileManager to perform a attributesOfItemAtPath:error: followed by removeItemAtPath:error:. I'm worried something will happen in between the two operations that invalidates the initial check.
What's the best way to make these two operations atomic?
Edit
The answers so far suggest file locking, which I have tried looking into. The closest thing I could find was setting the NSFileImmutable flag. But it seems like any other program could come along, unset it, and modify the file.. Is there a better way to lock a file?
Edit 2
Someone asked for a use case. Let's say I'm trying to keep two folders in sync. Any changes made to the files in one folder are mirrored in the other, and vice versa. If I delete file 1 from folder A, I will also delete file 1 from folder B. But if file 1 in folder B changes right before I delete it; then instead of deleting it, I want to sync it back to folder A
You can use mandatory (kernel enforced) file locking to lock the file in question to prevent changes being done to the file when you are operating on it. I know Linux and Solaris support mandatory file locking but I have no clue if OS X / HFS+ does and if so how to use it. Hope this helps.
So you have more than one attribute query then? If so, why not just lock the file before starting the queries? Once done, unlock. Then if delete, delete.
There's a way to lock a file with Cocoa; I googled and worked that problem a few days back, but I already forgot the specific message; sorry..
I suggest to use a message in order to accept or delete the file with this method:
fileManager:shouldRemoveItemAtPath:
The prototype of your development is to call method delete the file and in the method shouldRemoveItemAtPath: you accept (returns YES) or you reject (returns NO) as the file attributes values.
Hope this help
It seems to me that you should just go ahead and delete the files that matched. There's no point to locking unless you are worried some other app will change the file such that it can't be deleted. Think about it; you found a file that matches your delete criteria. You want to delete it. Does it really matter if it changes in the meantime?
I am developping a small file copy utility and I am using fscopyobjectasynch to copy files.
When a file already exists in the destination, I would like to ask the user if he want to keep the original file or to overwrite it.
I am trying to find a way to achive this whith fscopyobjectasynch
Thanks for your help
As stated in the documentation, FSCopyObjectAsync will overwrite an existing object at the destination if you give it the kFSFileOperationOverwrite flag. If you don't, it won't.
You can present an NSAlert to determine whether you should pass that flag.
I have a folder full of binary files and I want to make a change to these files so that the hash of these files will change. I want to do this is a fashion that doesn't pertinently corrupt the files. Meaning that the change should still allow the file to operate normally or that I should be able to undo the change at any point in time.
Does anyone know of a script that I could use to do this or many a program that will automate this?
Cheers
UPDATE
Its a edge case that I am trying to deal with. I have a system that only allows me to store a file with a given hash once. Hence I am wanting to change the content hash of the file to allow the file to be stored. Note the system in question is not one I control or can change.
Couldn't I just add a random 1 to the end of the file and then remove it afterward without breaking anything? I'm just not sure how to script this - as in how to modify the binary data in this way. Note I'm in a windows environment.
Without knowing the format of the files, we can't tell. It may in fact be impossible - for instance if these binary files are self-signed with some private key. Changing any single bit within the file is likely to render it invalid.
Is your hash calculated purely from the contents, and not any other metadata that you can change (such as filename or modified date)? If so, you're probably out of luck. If the hash is meant to detect when the content changes, but you're trying to change the hash without actually changing the content, you've clearly got a problem...
What is the hash used for? Why do you want to change it? There may be an alternative solution if you could give us more information about the bigger picture.
EDIT: One alternative is to effectively create your own container format - so while a file is stored in your container format, it's not usable in its original form, but it can be extracted easily. Your container could be as simple as "add four bytes at the end as a seed to disturb the hash" - "extracting" the file would just involve copying it and removing the last four bytes. But the important point is that what you end up with isn't an MP3 file or whatever you started with - it's your custom format, simple as it is. You need to package/extract the file any time you interact with the store.
On my site a user may upload a file (pic, zip, audio, video, whatever). He then may decide to replace it with a newer revision. This user may upload a file, make a post then decide to put up a new revision replacing the old (lets say its a large zip or tar.gz file). Theres a good chance people may be downloading it if he sent out an email or even im for the home user.
Problem. I need to replace the file and people may be downloading and it may be some minutes before it is deleted. I dont want my code to stall until i cant delete or check every second to see if its unused (especially bad if another user can start and he takes long creating a cycle).
How do i delete the file while users are downloading the file? i dont care if they stop i just care that the file can be replaced and new downloads are the new revision.
What about referencing the files indirectly?
A mapping script, maps a virtual file entry from your site to a real file . If the user wants to upload a new revision of his file you just update the mapping, not the real file.
You can install a daily task that scans all files and deletes all files without a mapping and without open connections.
lajuette's answer is right, the easiest solution is to work around the file locking altogether:
When a user uploads file foo.zip, internally store it as foo-v1.zip.
Create a mapping file somewhere (database, code, whatever) that maps foo.zip to foo-v1.zip.
Rather than exposing a direct link to the file, expose a link to a service that gets the file: mysite.com/Download?foo.zip or something. This service uses the mapping to determine which version of the file to send to the client.
When a new version is uploaded, create foo-v2.zip and update the mapping file.
It wouldn't be that hard to write a scheduled task that cleans up old, un-mapped files.
If your oppose to a database and If the filenames are in a fix format (such as user/id.ext) you could append the id with a revision number and enumerate the folder using a pattern (user/id-*) and use the latest revision.