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ioctl(2) [osf1 man page]

ioctl(2)							System Calls Manual							  ioctl(2)

NAME
ioctl - Controls devices SYNOPSIS
#include <stropts.h> int ioctl( int fildes, int request, ... /* arg */); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: ioctl(): XSH5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Specifies the file descriptor of the requested device. Specifies the ioctl command to be performed on the device. Specifies parameters for this request. The type of arg is dependent on the specific ioctl() request and device to which the ioctl is targeted. See the appro- priate Section 7 reference page or the documentation accompanying the device for more information. DESCRIPTION
The ioctl() function performs a variety of control functions on devices and STREAMS. For non-STREAMS files, the functions performed by this call are device-specific control functions. The request and arg parameters are passed to the file designated by fildes and are inter- preted by the device driver. This control is occasionally used on non-STREAMS devices, with the basic input/output functions performed through the read() and write() system calls. An ioctl() request has encoded in it whether the parameter is an "in" parameter or "out" parameter, and the size of the arg parameter in bytes. Macros and defines used to specify an ioctl() request are located in the <stropts.h> header file. For STREAMS files, specific functions are performed by the ioctl() function as described in streamio(7). STREAMS errors are described in streamio(7). RETURN VALUES
Upon successful completion, the ioctl() function returns a value other than -1 that depends upon the STREAMS device control function. If an error occurs, a value of -1 is returned and errno is set to indicate the error. ERRORS
The ioctl() function sets errno to the specified values for the following general conditions: The fildes parameter is not a valid open file descriptor. A signal was caught during the ioctl() operation. The STREAM or multiplexer referenced by fildes is linked (directly or indi- rectly) downstream from a multiplexer. If an underlying device driver detects an error, errno may be set to one of the following values: Either the request or arg parameter is not valid. Some physical I/O error has occurred. The fildes parameter is not associated with a STREAMS device that accepts control func- tions. (Defined for Issue 4 Version 2 and higher issues of the XSH specification.) [Tru64 UNIX] The fildes parameter is not associated with a character special device, or the specified request does not apply to the kind of object that the fildes parameter references. The request and arg parameters are valid for this device driver, but the service requested cannot be performed on the particular subdevice. The fildes parameter refers to a valid STREAMS device, but the corresponding device driver does not support the ioctl() function. RELATED INFORMATION
Functions: exec(2), fcntl(2) Files: tty(7), streamio(7) Standards: standards(5) delim off ioctl(2)

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IOCTL(2)						     Linux Programmer's Manual							  IOCTL(2)

NAME
ioctl - control device SYNOPSIS
#include <sys/ioctl.h> int ioctl(int d, int request, ...); DESCRIPTION
The ioctl() function manipulates the underlying device parameters of special files. In particular, many operating characteristics of char- acter special files (e.g., terminals) may be controlled with ioctl() requests. The argument d must be an open file descriptor. The second argument is a device-dependent request code. The third argument is an untyped pointer to memory. It's traditionally char *argp (from the days before void * was valid C), and will be so named for this discussion. An ioctl() request has encoded in it whether the argument is an in parameter or out parameter, and the size of the argument argp in bytes. Macros and defines used in specifying an ioctl() request are located in the file <sys/ioctl.h>. RETURN VALUE
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. ERRORS
EBADF d is not a valid descriptor. EFAULT argp references an inaccessible memory area. EINVAL Request or argp is not valid. ENOTTY d is not associated with a character special device. ENOTTY The specified request does not apply to the kind of object that the descriptor d references. CONFORMING TO
No single standard. Arguments, returns, and semantics of ioctl() vary according to the device driver in question (the call is used as a catch-all for operations that don't cleanly fit the UNIX stream I/O model). See ioctl_list(2) for a list of many of the known ioctl() calls. The ioctl() function call appeared in Version 7 AT&T UNIX. NOTES
In order to use this call, one needs an open file descriptor. Often the open(2) call has unwanted side effects, that can be avoided under Linux by giving it the O_NONBLOCK flag. SEE ALSO
execve(2), fcntl(2), ioctl_list(2), open(2), sd(4), tty(4) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2000-09-21 IOCTL(2)

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