I wrote a driver on linux, now i want to port it to freeRTOS, here i am getting trouble.
such as file handling API like fseek, opendir, readdir, fopen, fwrite, ftell how to find alternate in freeRTOS.
Take a look at this: FreeRTOS+IO.
But as you are referring to opendir(), readdir, etc, i suppose you need a File System library, and if it's the case, this is an excellent one : FatFs.
Should not be difficult to make FatFs work with FreeRTOS+IO.
Related
I come from C-family "mainstream" langages and i'm currently giving a try in Lua .
I made a simple code that check for a user entry and try to open an URL (built with user entry) in the default browser.
Saw the command os.execute("start "URL") that failed, saying that "os is undefined".
Well, seemed to be logical. I then researched the reason and discovered the "require" key word (which seems to act as a LoadLibrary or kind).
This is where I'm lost !
All forums says "yeah yeah just add require os and it will do". But it actually fail !
I obviously suspect that i am missing a "file" or path pointing at that "os" description. And that it's so obvious nobody found useful enough to explain or ask for it.
Can someone explain me what does require, in details ? Which file am i supposed to add (if i really need to ?).
If someone also have an online lesson to advise me, i'll accept it with pleasure. I feel like i'm missing a lot of basics and that's really not a "try to step-up" friendly langage
The standard Lua environment has os available without using require, so you must be using a non-standard Lua environment.
When Lua is embedded into different software, access to libraries like os is usually removed, as it is a security risk. (For example, if you allowed full access to the os library to anyone using Lua on a webserver, it would mean that anyone could run random shell commands on that server.)
If your Lua environment has been altered in this way, then there is a good chance that you will never be able to use the os library whatever you do.
I recently began looking into WebDAV, as I found it to be an option for letting me play a Blu-ray folder remotely - i.e. without requiring the viewer to download the whole 24gb ISO first.
Add a WebDAV source in Kodi v18 to a Blu-ray folder - and it actually plays! Very awesome.
The server can also be mounted on Windows with
net use m: http://example.com/webdavfolder/
or in Linux with
sudo mount -t davfs http://example.com/webdavfolder/ /mnt/mywebdav
-and should then (in theory) play with any software media players that supports Blu-ray Disc Java (BD-J), such as PowerDVD and VLC.
vlc bluray:///mnt/mywebdav --bluray-menu
PowerDVD.exe AUTOPLAY BD m:
(Unless of course time-out values has been set too low, which seems to be the case for VLC at the moment).
Anyway, all this is great, except I can't figure out how to make my WebDAV server read-only. Currently anyone can delete files as they wish, and that's of course not optimal.
So far I've only experimented with SabreDAV, because afaik that's the only option I have if I want to keep using my existing webhost. Trying with very minimal setups, because I've read that minimal setups should default to a read-only solution. It just doesn't seem to happen.
I initially used the setup from http://sabre.io/dav/gettingstarted/ and tried removing some lines. Also tried calling chmod 0444 MainFolder -R on the webserver. And I can see that everything does get a read-only attribute. But it changes nothing. It's still possible to delete whatever I want. :-(
What am I missing?
Maybe I'm using the wrong technology for what I want to do? Is there some other/better way of offering a Blu-ray folder for remote viewing? (One that includes the whole experience - i.e. full Java menus etc).
I should probably mention that all of this is of course perfectly legal. It is my own Blu-ray project - not copyright material.
Also: Difficult to decide if this belongs on StackOverflow or SuperUser. I ended up posting it on StackOverflow because SabreDAV is about coding, and because there's no sabredav tag on SuperUser.
You have two options:
Create your own file/directory classes for sabre/dav that simply throw an error when trying to delete. You can basically start with a copy of Sabre\DAV\FS\Directory and Sabre\DAV\FS\File and change the methods that do writing.
Since you're considering just using linux file permissions, really the key thing you are missing is that that 'deleting' is not controlled on the file or directory you're trying to delete. To delete a file or directory in unix, all you need is write permissions on the parent directory. However, I wouldn't recommend going this route as doing this will just cause a weird error in sabre/dav, which might leave clients in a confused state. It would result in a 500 error, not the expected 403 error.
I am trying to use the file:open(....) function in erlang but it doesn't seem to work. I keep getting an {error, eio} exception.
Ive looked into it in the erlang documentation and all i have found is that it is the posix error for input/output... go figure.
The file name im outputting in is in the formation of "C:/directory/file.txt"
Im not sure if this has something to do with it.
Is there anyway i can make erlang give me a more specific explanation to what is wrong?
Thanks,
Jack
Unfortunately I do not know of a way to find out more without peeking inside the Erlang/VM.
If you look in the windows erlang source code there are a bunch of different errors which could cause en eio error. You can find a list of them here. In order to figure out which specific one it is, I would attach with windbg and step through the code as instrumenting and recompiling it on windows is a pain.
You might also be able to use something like Process Monitor to find out which system calls are being made and what they return.
I am using someone else's library that provides its own scripting host instance, it appears.
This lib provides me with functions to define the type of scripting language such as "jscript" and "vbscript", and I can supply it with script code and have that executed, with passing arguments in and back. So, basically, it works.
However, when I try to access the "WScript" object, I get an exception saying that this keyword is undefined.
The developer, not knowing much about this either (he only made this lib for me because I do not want to deal with Windows SDKs right now), told me that he is using "IScriptControl" for this.
Oh, and the lib also provides flags to allow "only safe subset" and "allow UI", which I set to false and true, respectively.
Does that ring a bell with anyone? Do a user of IScriptControl have to take extra steps in order to make a WScript object available? Or, can he use IScriptControl in a way that this is supplied automatically, just as when running the same script from wscript.exe?
Basically, all I need is the WScript.CreateObject function in order to access another app's API via COM.
I don't know why WScript is not known, but I suspect it is because the script host doesn't provide it. Maybe only wscript.exe does this.
If you are using Javascript, to create an object you can use new ActiveXObject(). If you are using VBScript, you can just use CreateObject.
See this article for some background.
I want to write to/delete a file but sometimes I get a crash if the file is in use by another program. How do I check to see whether the file is opened by another process or I can open it for writing?
The problem is, that between the time you check to see if you could get exclusive access and opening the file, something else gets exclusive access to the file, and you get the exception anyway.
The only fool proof way to see if you can get an exclusive lock on a file is to try and get an exclusive lock on the file, if you get it you have it.
If not, you catch the exception, and either
Go do something else
Wait a while and try again
It's one of life’s situations where it's better to ask for forgiveness than permission :)
There is a new way to get the origin of file locking for Vista and up here:
http://www.remkoweijnen.nl/blog/2011/01/03/cannot-access-files-but-need-the-origin/
UserMode:
The best way to write to a locked file is to ask the user to close it in the other process. In batch processes you should ignore such a file and log the problem. Providing the name of the other process is a very good way to find a solution for the user.
Not sure in which programming language you'd like to check if you can write to a file. In Java, java.io.File.canWrite() can do the job for you.
General:
In UNIX-like OS, you can use the lsof command.
If you want to see which program holds a handle to your file, use the Process Monitor (download from MicroSoft).
This tool has a command line interface, so you could use your language's scripting interface (for example java.lang.Process) to run the tool and display a useful error message.
IsFileInUse as given in http://delphi.about.com/cs/adptips1999/a/bltip0999_3.htm