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.

Debian                                            July 24, 1996                                      VOP_RDWR(9)