Question: What Is An Ioctl Call?

Where is ioctl defined?

Macros and defines used in specifying an ioctl() request are located in the file .

How does ioctl work in Linux?

An ioctl , which means “input-output control” is a kind of device-specific system call. There are only a few system calls in Linux (300-400), which are not enough to express all the unique functions devices may have. So a driver can define an ioctl which allows a userspace application to send it orders.

Is ioctl thread safe?

ioctl() is not one of them, so it IS thread-safe. However, ioctl() is a cancellation point, so the thread can be terminated once it reaches ioctl().

How do you pronounce ioctl?

Like the Linux ioctl. Pronounced “i-oct-el”.

Is ioctl blocking call?

In addition to SELECT, applications can use the IOCTL or FCNTL calls to help perform asynchronous (nonblocking) socket operations. The IOCTL call has many functions; establishing blocking mode is only one of its functions. The value in COMMAND determines which function IOCTL will perform.

What does ioctl return?

Usually, on success zero is returned. A few ioctl() requests use the return value as an output parameter and return a nonnegative value on success. On error, -1 is returned, and errno is set appropriately.

What is ioctl error?

In computing, ioctl (an abbreviation of input/output control) is a system call for device-specific input/output operations and other operations which cannot be expressed by regular system calls. It takes a parameter specifying a request code; the effect of a call depends completely on the request code.

What does Sysctl stand for?

sysctl is a software utility of some Unix-like operating systems that reads and modifies the attributes of the system kernel such as its version number, maximum limits, and security settings.

What is Unix file descriptor?

In Unix and related computer operating systems, a file descriptor (FD, less frequently fildes) is an abstract indicator (handle) used to access a file or other input/output resource, such as a pipe or network socket. File descriptors form part of the POSIX application programming interface.

What is inappropriate ioctl for device?

“inappropriate ioctl for device” is the error string for the ENOTTY error. … More generally, it is triggered when doing an ioctl on a device that does not support that ioctl, hence the error string. To find out what ioctl is being made that fails, and on what file descriptor, run the script under strace/truss.

What is Dev Net Tun?

1. Description TUN/TAP provides packet reception and transmission for user space programs. … If you want to create persistent devices and give ownership of them to unprivileged users, then you need the /dev/net/tun device to be usable by those users.