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34 .\" @(#)ioctl.2 6.4 (Berkeley) 3/10/91
36 .\" Modified 1993-07-23 by Rik Faith <faith@cs.unc.edu>
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41 .TH IOCTL 2 2000-09-21 "Linux" "Linux Programmer's Manual"
43 ioctl \- control device
45 .B #include <sys/ioctl.h>
47 .BI "int ioctl(int " d ", int " request ", ...);"
51 function manipulates the underlying device parameters of special files.
52 In particular, many operating characteristics of character special files
53 (e.g., terminals) may be controlled with
58 must be an open file descriptor.
60 The second argument is a device-dependent request code.
61 The third argument is an untyped pointer to memory.
66 was valid C), and will be so named for this discussion.
71 has encoded in it whether the argument is an
75 parameter, and the size of the argument
78 Macros and defines used in specifying an
81 are located in the file
84 Usually, on success zero is returned.
87 requests use the return value as an output parameter
88 and return a nonnegative value on success.
89 On error, \-1 is returned, and
96 is not a valid descriptor.
100 references an inaccessible memory area.
110 is not associated with a character special device.
113 The specified request does not apply to the kind of object that the
119 Arguments, returns, and semantics of
121 vary according to the device driver in question (the call is used as a
122 catch-all for operations that don't cleanly fit the UNIX stream I/O
126 for a list of many of the known
131 function call appeared in Version 7 AT&T UNIX.
133 In order to use this call, one needs an open file descriptor.
136 call has unwanted side effects, that can be avoided under Linux