errno(9) [netbsd man page]

ERRNO(9)						   BSD Kernel Developer's Manual						  ERRNO(9)

NAME

     errno -- kernel internal error numbers

SYNOPSIS

     #include <sys/errno.h>

DESCRIPTION

     This section provides an overview of the error numbers used internally by the kernel and indicate neither success nor failure.  These error
     numbers are not returned to userland code.

DIAGNOSTICS

     Kernel functions that indicate success or failure by means of either 0 or an errno(2) value sometimes have a need to indicate that
     ``special'' handling is required at an upper layer or, in the case of ioctl(2) processing, that ``nothing was wrong but the request was not
     handled''.  To handle these cases, some negative errno(2) values are defined which are handled by the kernel before returning a different
     errno(2) value to userland or simply zero.

     The following is a list of the defined names and their meanings as given in <errno.h>.  It is important to note that the value -1 is not
     used, since it is commonly used to indicate generic failure and leaves it up to the caller to determine the action to take.

     -2 EJUSTRETURN Modify regs, just return.  No more work is required and the function should just return.

     -3 ERESTART Restart syscall.  The system call should be restarted.  This typically means that the machine dependent system call trap code
	     will reposition the process's instruction pointer or program counter to re-execute the current system call with no other work
	     required.

     -4 EPASSTHROUGH Operation not handled by this layer.  The operation was not handled and should be passed through to another layer.  This
	     often occurs when processing ioctl(2) requests since lower layer processing may not handle something that subsequent code at a higher
	     level will.

     -5 EDUPFD Duplicate file descriptor. This error is returned from the device open routine indicating that the l_dupfd field contains the file
	     descriptor information to be returned to the caller, instead of the file descriptor that has been opened already.	This error is used
	     by cloning device multiplexors.  Cloning device multiplexors open a new file descriptor and associate that file descriptor with the
	     appropriate cloned device.  They set l_dupfd to that new file descriptor and return EDUPFD.  vn_open(9) takes the file descriptor
	     pointed to by l_dupfd and copies it to the file descriptor that the open call will return.

     -6 EMOVEFD Move file descriptor. This error is similar to EDUPFD except that the file descriptor in l_dupfd is closed after it has been
	     copied.

SEE ALSO

     errno(2), ioctl(9)

HISTORY

     An errno manual page appeared in Version 6 AT&T UNIX.  This errno manual page appeared in NetBSD 3.0.

BSD
								 December 3, 2004							       BSD

Check Out this Related Man Page

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 3.27 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)

Linux and UNIX Man Pages

errno(9) [netbsd man page]

Check Out this Related Man Page