errno(9) - NetBSD Manual Pages

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ERRNO(9)               NetBSD 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'' han-
     dling is required at an upper layer or, in the case of ioctl(2) process-
     ing, that ``nothing was wrong but the request was not handled''.  To han-
     dle these cases, some negative errno(2) values are defined which are han-
     dled by the kernel before returning a different errno(2) value to user-
     land 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
             arranges for it to be copied 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.

NetBSD 10.1                    December 3, 2004                    NetBSD 10.1