I have, so far, successively emit and view data from yaml file, but I can't modyfy it. I did try to overwrite sth, but it didn't work. For deleting, I thought that I can load whole file to a variable, and then using std::string and regexp, procces it, and send it back, but it's not satisfactory, clean or "nice". What should I do?
You can't do that directly with yaml-cpp; your best bet is to read it into your own data structure, modify that data, and then emit it.
Related
save is used to store data in a format more directly usable by REBOL, as stated here
write has an append mode but it saves data in a raw mode.
My application needs to save a block of data (as a map!) to disk. Each couple of seconds it will generate a new element, up to tens of thousand of elements.
So, my question. I can save the whole data each couple of seconds. But I'd like to know if I can append the new elements to disk using the save command or save format. I guess that I could mimic the save format using the write command in /append mode. Is this the best solution, or is there another one I don't know?
save is a mezzanine function, that is basically write mold. So it's possible to mimic the save function using write or it's possible to update save function to support /append refinement.
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.
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?
How do I undo an update in Accurev? I want to revert to a state where contents of the files are exactly how it was before an "update" operation?
There are numerous ways to change the contents in your workspace to reflect an earlier configuration. Based on the limited description where you reference "all the files under CM", I'll make the assumption that you want to roll back your entire workspace as opposed to a select few files.
Question: does everyone parented by the same stream as your workspace want to roll back, or just you? If it's everyone, you can change the time basis of that parent stream to reflect the specific point in time you want to revert to. Once that is done, run Update, and you're good. If it's just you and it's more than a small sampling of files, I'd suggest creating a personal time-based stream, setting the time to when you want, and re-parenting your workspace to it:
Current_parent -- New_personal_time_stream -- your_workspace
There are other options as well if you just want to deal with a few select files, but it seems like this is what you're after...
Cheers,
~James
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.