The /dev/null file is not a character device file

Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation. Details required : characters remaining Cancel Submit 2 people found this reply helpful. I had a lot of problems with Composer on Windows as well as Git recently, same as Larry mentioned. And compared it with my co-worker configuration. We found out that there is a difference in "Start" key, which value was set to 4 for me and 1 for my friend.

I'm not sure if setting it to 1 the hard way will fix it, but I have fixed that by downloading default Null settings from here. I hope it helps you. If it works, spread this solution if you want, just because I saw a lot of requests on it regarding Git for example. Any clues? You need to define some magic numbers used as CMD and probably as ARG somewhere in a separate header file, shared between driver code and user application code.

All implementation of the ioctl function is a simple switch case routine where you do something depending on the sent CMD. Now a complete example of the Linux kernel module, which implements everything that we were discussed here. I hope this material will be helpful. This code can be used as a basic pattern in some more complex driver project.

Hi dear Oleg I have question about how to implement this kind of char device driver. Create a kernel character device driver which will:. Everything you writing to the character device is just a byte stream, without additional information.

There are several ways to configure this limit if you need it. It can be some custom IOCTL, or special command, written to the character device before data writing. All future data you interpret just like a binary stream. Hi thank you for your message, I really newcomer to linux kernel and driver programming I understand that it realization is very easy, but for me problem is to understand can you give some solution of this task.

I really please you about that. Could you please point me below things 1 platform devices and drivers program linked with device tree. Also, using maxdatalen to declare the size of databuf is doing things backwards. I run on raspberry pi. Hello from the kernel world!

In my example, there is a specifier of the expected buffer length: head -c29 This command reads 29 bytes and exits. But this is just a bad synthetic example. Be careful in real-world applications. Really you should always read some valid data length, verify this length in a driver function and always return the real size of the data.

Then handle read count in the top-level code. Also, even on those systems users could just avoid saving files to the same file name and there won't by any problems.

I'm sure users on systems without ftruncate have similar problems all the time Just to reiterate I don't see how this is better than checking if the filename is a device beforehand and if so don't unlink. In either case there's potential for a race condition and this way it's at least more straightforward. What I don't understand, then, is the following: if you don't know of a system without ftruncate , then why do you detect the feature?

And then, if an issue pops up where curl doesn't build on Baddix because Baddix lacks ftruncate , then is the time to wonder: is Baddix worth supporting? Can reasonable, non-buggy behaviour be obtained without ftruncate , and how much effort does it require? Would people who want to use curl on Baddix be willing to contribute the necessary workaround?

That said, I totally share your pain wrt the amount of broken, incomplete systems out there. I have a whole general-purpose library to perform all the system-dependent workarounds I need; I don't even attempt to support Windows, but even getting the BSDs to work is a lot of annoyance. One thing the locking improves is for situations where the application only has the permission to write to the file but not to change the directory, so a rename isn't allowed.

Skip to content. Star New issue. Jump to bottom. Copy link. On Sun, Apr 11, at AM , rofl0r wrote And as mentioned in here, it should be changed No good reason I think.

This makes them work properly when the output is a character device. Applies to cookies, alt-svc and hsts files. Reported-by: rofl0r on github Assisted-by: Paul Vixie Fixes Every time you log in or launch a new xterm, a tty device is assigned to the shell. This device is responsible for displaying the shell's output and providing its input.

It is known as the controlling tty for that shell and its child processes. Console ttys are used when the keyboard and monitor are directly connected to the system without running the X Window System. Since you can have several virtual consoles, the devices are tty0 through tty In theory you can have 64 virtual consoles, but most people use only a few. If you have a terminal connected to a serial port or if you dial in using a modem, you'll use a serial tty device. This begins to get confusing, because there are also callout devices for each serial port.

For each ttyS device there is a corresponding cua device. If you're only using the serial port for one purpose, it probably doesn't matter which device you use.

To be able to both dial in to your machine remotely and dial out when you're home, be sure to use the tty version of the device to listen for incoming calls and the callout version to place outgoing calls. By doing this, you won't mess up someone who has dialed in by trying to dial out on the same line. Pseudo tty devices are used when a login is initiated by launching a new xterm or by connecting to your machine via TELNET. Because you can have lots of windows open and many TELNET sessions going on at one time, you may need a lot of these devices.

Originally, Linux limited you to 64 pseudo terminals, but some people found that too restrictive, so you can now have up to of them, using different major and minor device numbers.

Making it a bit more complicated, there are actually two devices for each pseudo tty: a master and a slave. Fortunately, you don't have to worry about the distinction other than being careful to create or delete them in pairs. If you wish to get every possible millisecond out of your system, there are a few things you should know about directories in UNIX file systems.