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

NAME

     VOP_READ, VOP_WRITE -- read or write a file

SYNOPSIS

     #include <sys/param.h>
     #include <sys/vnode.h>
     #include <sys/uio.h>

     int
     VOP_READ(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred);

     int
     VOP_WRITE(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred);

DESCRIPTION

     These entry points read or write the contents of a file

     The arguments are:

     vp      The vnode of the file.

     uio     The location of the data to be read or written.

     ioflag  Various flags.

     cnp     The credentials of the caller.

     The ioflag argument is used to give directives and hints to the file system.  When attempting a read, the high 16 bits are used to provide a
     read-ahead hint (in units of file system blocks) that the file system should attempt.  The low 16 bits are a bit mask which can contain the
     following flags:

     IO_UNIT	    Do I/O as atomic unit.

     IO_APPEND	    Append write to end.

     IO_SYNC	    Do I/O synchronously.

     IO_NODELOCKED  Underlying node already locked.

     IO_NDELAY	    FNDELAY flag set in file table.

     IO_VMIO	    Data already in VMIO space.

LOCKS

     The file should be locked on entry and will still be locked on exit.

RETURN VALUES

     Zero is returned on success, otherwise an error code is returned.

ERRORS

     [EFBIG]		An attempt was made to write a file that exceeds the process's file size limit or the maximum file size.

     [ENOSPC]		The file system is full.

     [EPERM]		An append-only flag is set on the file, but the caller is attempting to write before the current end of file.

SEE ALSO

     uiomove(9), vnode(9)

AUTHORS

     This manual page was written by Doug Rabson.

BSD
								   July 24, 1996							       BSD