shared | Shared resources of db-migrate | Database library
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kandi X-RAY | shared Summary
Shared resources of db-migrate.
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QUESTION
I understand that after calling fork() the child process inherits the per-process file descriptor table of its parent (pointing to the same system-wide open file tables). Hence, when opening a file in a parent process and then calling fork(), both the child and parent can write to that file without overwriting one another's output (due to a shared offset in the open-file table entry).
However, suppose that, we call open() on some file after a fork (in both the parent and the child). Will this create a separate entries in the system-wide open file table, with a separate set of offsets and read-write permission flags for the child (despite the fact that it's technically the same file)? I've tried looking this up and I don't seem to be able to find a clear answer.
I'm asking this mainly since I was playing around with writing to files, and it seems like only one the outputs of the parent and child ends up in the file in the aforementioned situation. This seemed to imply that there are separate entries in the open file table for the two separate open calls, and hence separate offsets, so the slower process overwrites the output of the other process.
To illustrate this, consider the following code:
...ANSWER
Answered 2021-May-03 at 20:22There is a difference between a file and a file descriptor (FD).
All processes share the same files. They don't necessarily have access to the same files, and a file is not its name, either; two different processes which open the same name might not actually open the same file, for example if the first file were renamed or unlinked and a new file were associated with the name. But if they do open the same file, it's necessarily shared, and changes will be mutually visible.
But a file descriptor is not a file. It refers to a file (not a filename, see above), but it also contains other information, including a file position used for and updated by calls to read and write. (You can use "positioned" read and write, pread and pwrite, if you don't want to use the position in the FD.) File descriptors are shared between parent and child processes, and so the file position in the FD is also shared.
Another thing stored in the file descriptor (in the kernel, where user processes can't get at it) is the list of permitted actions (on Unix, read, write, and/or execute, and possibly others). Permissions are stored in the file directory, not in the file itself, and the requested permissions are copied into the file descriptor when the file is opened (if the permissions are available.) It's possible for a child process to have a different user or group than the parent, particularly if the parent is started with augmented permissions but drops them before spawning the child. A file descriptor for a file opened in this manner still has the same permissions uf it is shared with a child, even if the child would itself be able to open the file.
QUESTION
I have a dataset with various "chunks" of columns with different prefixes, but the same suffix:
ID A034 B034 C034 D034 A099 B099 A123 B123 ... 1 NA 1 NA NA NA 3 1 NA ... 2 2 NA NA NA 2 NA NA 2 ... 3 NA NA 2 NA NA 2 1 NA ...The number of columns within each "chunk" also varies. Is there any way (other than manually, which is what I have been painstakingly doing with coalesce(!!! select(., contains("XXX")))) to automatically coalesce by chunk based on the shared suffix? That is, the result should resemble
I'm not sure how to begin doing something like this, so any suggestions would be very helpful.
...ANSWER
Answered 2021-Jun-15 at 20:10We reshape the data into 'long' format with pivot_longer, then we group by 'ID' and loop across the other columns, apply the na.omit to remove the NA elements (we assume that there is only one non-NA per each column by group)
QUESTION
I am pretty new to python and I am trying to sort through a directory's files that start with 'O0' and copy any string in the text files that has an 'F', 'T', or 'S' in them, and paste, preferably just that string, (but the whole line would still work) in a new text file, preferably on the desktop. It is making the text file, but it is blank, and python does not close the file. Here's what I have so far:
...ANSWER
Answered 2021-Jun-15 at 14:27In the first place you are probably getting an AttributeError error that append is not known. Because you try to append your text to the TextIOwrapper (feeds speeds). You have to use the write method to append the text to the file content.
Also note that your file is read and written from the current directory, so ./feedsspeeds.txt. As long as you are not executing this script from you Desktop folder, the file will also not be written there.
QUESTION
I use the following code to update my widget's timeline, but the "result" which I fetched from the core data is not up-to-date.
My logic is when detecting the host app goes to background I call "WidgetCenter.shared.reloadAllTimelines()" and fetch the core data in the "getTimeline" function. After printing out the result, it is old data. Also I fetch the data with the same predicate under the .background, the data is up-to-date.
Also I show the date in the widget view body, when I close the host app, the date is refreshing. Means that the upper refreshing logic works fine. But just always get the old data.
Could someone help me out?
...ANSWER
Answered 2021-Jun-15 at 17:05Update:
I added the following code to refresh the core data before I fetch. Everything work as expect.
QUESTION
I am attempting to write a a UI test that taps on a delivered local notification after the device has been locked. I have been successful so far in tapping on a notification that was delivered on the springboard (when the device is already unlocked) but not from the lock screen. Does anyone know if this is possible?
Please note that this is different from questions such as this one, which merely hit the home button to leave the app under test and wait for the notification.
Here is the relevant portion of my test code:
...ANSWER
Answered 2021-Jun-15 at 14:49I have similar issues, and I was able to resolve them by Adding a press lock Again. Here is the working code. I am using https://github.com/pterodactyl for Notifications. I wrote this code a couple of years back and still passing.
I do the same thing twice and able to validate notifications. Once the device is locked. You will see a black screen like it is turned off, and the second time when you will send the same code, it will turn on the device, and you can get notifications element for tests
// Lock the screen
XCUIDevice.shared.perform(NSSelectorFromString("pressLockButton"))
sleep(1)// same command second time ,it will wake the screen
XCUIDevice.shared.perform(NSSelectorFromString("pressLockButton"))
QUESTION
I have a table in SQL Server 2008 database hosted on a shared web hosting. I cannot change the collation of the database because I don't have permissions.
When I created the table, I set the collation for the columns that I want but it doesn't do anything and I still see ???? when I query the table. I tried nvarchar as well and it didn't work.
The table:
...ANSWER
Answered 2021-Mar-25 at 20:05The problem is your INSERT/UPDATE statements. Unless you define those values as an nvarchar then the characters outside the databases collation will be lost. This means you need to declare your parameters as an nvarchar. As a result I would suggest, instead, not changing the collation of the columns and changing them as an nvarchar and using an nvarchars throughout your code.
QUESTION
I'm doing a Group Chat with Firebase and currently I'm using a RecyclerView to display chat messages and I'm having a problem. When you open the app in the fragmented home and you go to chat activity and start chatting (adding elements to recycler view) all goes fine. But, when you go via the NavigationDrawer to another fragment and get back to the chat fragment using again this Navigation Drawer. When you add one element in the chat it appears all in the blank it just displays the last message. Anybody knows why does this happens?
Here I leave the RecyclerView Adapter Code:
...ANSWER
Answered 2021-Jun-15 at 13:55To solve your problem you can just remove the OnResume method because you are initializing the array every time you change between fragments and that is the problem.
QUESTION
So, I am working on an MVVM-based core SDK for use any time I am developing some Google Apps Script based software, called OpenSourceSDK. It contain core business logic, including base classes to extend. For example, the file Models/BaseModel.gs in it is defined to be:
ANSWER
Answered 2021-Jun-13 at 22:53I was able to get it resolved, but the solution is...hacky.
So, apparently, Google Apps Script exports only what is in globalThis of a project: just the functions and variables. No classes, no constants, ...
Probably has a lot to do with how ES6 works, with its globalThis behavior. One can see that in action, by creating a dummy function, a dummy variable, and a dummy class in their local developer console:
QUESTION
I have a winform application that sometimes needs to log info to a local file when connection to service is broken. After reconnect all log files will be sent to the service for logging in database. Because the log is stored in the root of the application folder it can be read by other user accounts of the computer. So if user A that gets an exception do not have connection to the service the content of the logfile from user A will be sent when user B connects to the service.
The problem is that some users to not give write permissions to the root folder.
There is special user folders that could be used but the problem is that user B will not be able to send user A log file to service.
Is there any shared Windows folder where I always can write? Or do I have to require write permission of the root of the application?
Regards
...ANSWER
Answered 2021-Jun-15 at 09:44If you want to write logs for the per User that the application is started as, I would write them in AppData, but if you want to store logs that is global to your application I would write the logs in ProgramData.
In C# you can get these special folders with Environment.GetFolderPath and passing as an argument the desired Environment.SpecialFolder.
QUESTION
I designed an App that holds a stack of layers and an active obj.
When a Layer is attached to the App, the Layer tells App what an active object is. But my design causes a sigtrap when deallocating.
It cause sigtrap because the destruction of shared_ptr m_obj in App happens first which reduce the use_count to 1. Then the onDetech function gets call, setting the active shared_ptr m_obj to nullptr and reduce use_count to 0! But the layer still holds an shared_ptr.
The code below is a minimal example to reproduce. I notice my code has a reference cycle but I have no idea how to fix this except using a raw pointer for obj in the App class.
I used shared_ptr for obj in App because it makes sense to me that App has the shared ownership of obj. Should I not use shared_ptr in this case?
ANSWER
Answered 2021-Jun-15 at 04:42You're accessing m_activeObj after its lifetime has ended, and thus the behavior of your program is undefined.
The sequence of events is as follows:
Appobject goes out of scope~Apprunsm_activeObjis destroyed; after this its lifetime has ended and it can no longer be accessedm_defaultLayeris destroyedm_stackis destroyedm_layers[0].onDetach()is calledonDetachsetsm_app->m_activeObjtonullptr, but its lifetime has already ended, so behavior is undefined.
- Irrelevant other stuff; you're already screwed.
The solution is to reorder things so that you don't access m_activeObj after its lifetime has ended. Either move m_stack's declaration after m_activeObj so it gets destroyed first or clear it manually in ~App.
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