Neither io nor lfs seem to have an option to check for this. I need to use this feature to simulate some code that does this check.
It seems there's an undocumented permissions field in the table returned by lfs.attributes(). Thanks to #siffiejoe for pointing this out, didn't see it when I read the code.
Another approach is of course to try to read from the file, that will always work but might be slower.
You could also try opening the file and setting a (temporary, of course) read lock on it. Not sure about the portability of file locking in Lua, though.
Note: checking if a file is readable and then doing something can break due to race conditions; the permissions of a file can change between your check and the following action.
Related
I have this iOS module that creates and writes to some plist files in NSApplicationSupportDirectory, and I'd like to test that the module is performing these writes correctly. However, the writes don't seem to be going through - after calling the module method, the file seems to not exist. I've also tried writing to the desired file directly from the unit test module, and that doesn't seem to do anything either - using NSDictionary writeToFile returns NO, indicating that the write failed.
Is it impossible to write to this directory from a unit test environment, or is it more likely that I just screwed something up? And if it is indeed impossible to perform this write, what would the proper way to test this behavior be? If anyone needs more details, I'd be happy to provide them.
Thanks!
Discovered my own error: The NSApplicationSupportDirectory simply doesn't exist by default (this is why the write is failing). You need to create the directory before you can use it. See this post:
iOS: Can't save file to 'Application Support' folder, but can to 'Documents'
i have an iOS App which loads and .txt file from app's root. If i use iFunBox or any iPhone Browsers i can see that .txt file, how can I hide it? I think it's all about security of this file, encode/decode. Please help me. Any advice, source codes, examples. I'm new here. thanks
The short answer: You can't
The long answer: No matter what you do, you will end up having a copy of the decrypted contents in memory at some point so a crafty cracker will be able to copy the contents out of memory. The best you can do is make it not worth their trouble. This includes using pure C, never storing the contents in one variable (always concat, etc), and encrypting the file with an industry standard encryption like AES-256. Good luck.
I'm not sure that it is possible to protect the file any more than what apple already does. Even if you could, I don't think It would really be worth your trouble to do so unless the .txt file is something that you really need to protect.
I'm interested in some information inside a shadow file (.shd) located inside the windows print spooling directory "C:\Windows\System32\spool\PRINTERS". Every time a print job is started, a spool file (.spl) and a shadow file (.shd) are created in that directory. So far I have been successful in detecting when a print job has started, and have been able to pause that print job. If you don't pause the job, the files eventually make their way to the printer and then are deleted by windows.
My problem is. I cannot open the .SHD files because they are locked in such a way that you can not read them while they are open by the sprint spooler. I've even tried going to the file in windows explorer and simply copying the file to another file, and that didn't work either. The .SPL spool files I can open though. I simply wait, and fairly quickly the spooler release that file. For the shadow file though, it permanently holds on to this file. Unfortunately, its the one I need.
The line of code I'm using specifically to open the file is as follows:
m_spoolJobStream = new FileStream(spoolFilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
The IOException I get is:
The process cannot access the file 'C:\Windows\system32\spool\PRINTERS\FP00083.SHD' because it is being used by another process.
So yes, it is being used by another process. Its being used by the window's print spooler service. But I don't think there is anything I can do about that. All I want to do is read the file. I don't want to make any changes to it. Is there anything I can do here or am I just screwed?
Check the option: "Keep printed documents" (if you have HP printer) and then see your spool file folder, both shadow and spool files would be there.
Well, I did not find a way around this problem. I suspect there is no solution for this and it is by design. However I did find another way to get the information I wanted (at least it seems so thus far).
I'm using the FindNextPrinterChangeNotification() routine out of the winspool.drv library. This guy returns a pointer to a PRINTER_NOTIFY_INFO structure, which in turn contains an array of PRINTER_NOTIFY_INFO_DATA structures. Within that array, there is an element with its "Field" member marked as "JOB_NOTIFY_FIELD_DEVMODE". This element contains a fairly large structure of type DEVMODE. The structure is explained by M$ here http://msdn.microsoft.com/en-us/library/dd183565%28v=vs.85%29.aspx . This structure looks like it contains what I'm looking for and apparently is wrapped up in the .SHD file anyways according to this page http://www.undocprint.org/formats/winspool/shd. I'd like to know what else is in that .SHD file, but I still can't open it because its locked while the job is paused, and I suspect that it stays locked until the job is complete. Oh well, I think my new solution is more elegant anyways.
Just make sure you pause the job in the spool on BOTH your box and the server, then you should be able to copy/open/move the shd file just like you can the spl file. Worked for me, anyway...
This works for me:
- Hang your printer (e.g. jam the paper)
- Print and observe .SHD and .SPL being created
- Stop Print Spooler
- Open the file
The problem might be the FileShare.ReadWrite parameter. You're asking to read and write on the file and maybe that's why you get an error. You should try asking for read-only permission.
I am getting file list in my Java program using list() method of File class. When I run my program on Knoppix I get ???? instead of Cyrillic file names. It seems that problem is in knoppix, not java. I tried to use options for mounting file system, such as nls and iocharset, but it has no effect (or may be I use it in wrong way). Somebody can help me?
I think that problem is as you said with Knoppix. Probably you do not have Cyrillic font bundled, so there is no way to display these code points.
If you want to fix this, you will need fix distribution, as there is nothing wrong with the program. I am not sure if this is the question for https://serverfault.com/ or https://superuser.com/, but you can read their FAQ's and ask how to fix it there (probably you will need to re-create Knoppix distribution).
Sometimes when I add a new file to my path, I have to restart MATLAB or it won't be detected. There must be an other way to this!
I have experienced similar problems (Matlab does not notice it when I change a file). Unfortunately, I have no idea what causes it or how to solve it. I usually find that CLEAR ALL solves the problem, but be aware that it clears all variables in the work space. Some 'REHASH' command (e.g., REHASH TOOLBOXRESET) may also be useful.
I'd love to see a better answer; all documentation that I came across seems to indicate that this cannot happen.
Perhaps this is a problem with Matlab caching certain files at startup to improve performance. This happens with files in certain directories.
From Matlab help for path command:
Note (...) Also note that locations of files in the matlabroot/toolbox directory tree are loaded and cached in memory at the beginning of each MATLAB session to improve performance. If you save files to matlabroot/toolbox directories using an external editor or add or remove files from these directories using file system operations, run rehash toolbox before you use the files in the current session. If you make changes to existing files in matlabroot/toolbox directories using an external editor, run clear functionname before you use the files in the current session. For more information, see the rehash reference page or the Toolbox Path Caching topic in the MATLAB Desktop Tools and Development Environment documentation
I've often seen this happen with networked file locations. I don't understand the mechanism, but it definitely happens. A solution that often works:
path(path);
or, if that fails to pick it up, try this: (NB, this will clear your workspace)
clear classes;
path(path);
We did this last one so much, we put it in script on our common code path called:
shazaam;
Yes, my age is showing.
You want the "rehash" function or you need to set the path again using "path(path)" or similar. It also depends on whether you're using a "frozen" path. Look at the help for ADDPATH.
MATLAB will keep a cached copy of the compiled M-file unless it know that you've changed it. If you've created the file or you've edited it outside of MATLAB, then it may not know that it's changed.
This happens to me when the networked drive connection is lost then restored. rehash does not work but rehash toolboxreset does