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All Rights Reserved. .\" .TH IOCTL 2 "June 18, 2020" .SH NAME ioctl \- control device .SH SYNOPSIS .nf #include #include \fBint\fR \fBioctl\fR(\fBint\fR \fIfildes\fR, \fBint\fR \fIrequest\fR, \fB/*\fR \fIarg\fR */ ...); .fi .SH DESCRIPTION The \fBioctl()\fR 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 \fIrequest\fR argument and an optional third argument with varying type are passed to the device file designated by \fIfildes\fR and are interpreted by the device driver. .sp .LP For streams files, specific functions are performed by the \fBioctl()\fR function as described in \fBstreamio\fR(4I). .sp .LP The \fIfildes\fR argument is an open file descriptor that refers to a device. The \fIrequest\fR argument selects the control function to be performed and depends on the device being addressed. The \fIarg\fR argument represents a third argument that has additional information that is needed by this specific device to perform the requested function. The data type of \fIarg\fR depends upon the particular control request, but it is either an \fBint\fR or a pointer to a device-specific data structure. .sp .LP In addition to device-specific and streams functions, generic functions are provided by more than one device driver (for example, the general terminal interface or disk interfaces.) See \fBtermio\fR(4I)), \fBdkio\fR(4I), etc.. .SH RETURN VALUES Upon successful completion, the value returned depends upon the device control function, but must be a non-negative integer. Otherwise, \fB\(mi1\fR is returned and \fBerrno\fR is set to indicate the error. .SH ERRORS The \fBioctl()\fR function will fail for any type of file if: .sp .ne 2 .na \fB\fBEBADF\fR\fR .ad .RS 10n The \fIfildes\fR argument is not a valid open file descriptor. .RE .sp .ne 2 .na \fB\fBEINTR\fR\fR .ad .RS 10n A signal was caught during the execution of the \fBioctl()\fR function. .RE .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 10n The stream or multiplexer referenced by \fIfildes\fR is linked (directly or indirectly) downstream from a multiplexer. .RE .sp .LP The \fBioctl()\fR function will also fail if the device driver detects an error. In this case, the error is passed through \fBioctl()\fR without change to the caller. A particular driver might not have all of the following error cases. Under the following conditions, requests to device drivers may fail and set \fBerrno\fR to indicate the error .sp .ne 2 .na \fB\fBEFAULT\fR\fR .ad .RS 11n The \fIrequest\fR argument requires a data transfer to or from a buffer pointed to by \fIarg\fR, but \fIarg\fR points to an illegal address. .RE .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 11n The \fIrequest\fR or \fIarg\fR argument is not valid for this device. Many devices return \fBENOTTY\fR for an unknown \fIrequest\fR. .RE .sp .ne 2 .na \fB\fBEIO\fR\fR .ad .RS 11n Some physical I/O error has occurred. .RE .sp .ne 2 .na \fB\fBENOLINK\fR\fR .ad .RS 11n The \fIfildes\fR argument is on a remote machine and the link to that machine is no longer active. .RE .sp .ne 2 .na \fB\fBENOTTY\fR\fR .ad .RS 11n The \fIfildes\fR argument is not associated with a device that accepts control functions. .sp The device driver does not know the \fIrequest\fR command. .RE .sp .ne 2 .na \fB\fBENXIO\fR\fR .ad .RS 11n The \fIrequest\fR and \fIarg\fR arguments are valid for this device driver, but the service requested can not be performed on this particular subdevice. .sp The device driver does not support the \fBioctl()\fR function. .RE .sp .ne 2 .na \fB\fBENODEV\fR\fR .ad .RS 11n The \fIfildes\fR argument refers to a valid streams device, but the corresponding device driver does not support the \fBioctl()\fR function. .RE .sp .LP Streams errors are described in \fBstreamio\fR(4I). .SH ATTRIBUTES See \fBattributes\fR(7) for descriptions of the following attributes: .sp .sp .TS box; c | c l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Standard .TE .SH SEE ALSO .BR streamio (4I), .BR termio (4I), .BR attributes (7), .BR standards (7)