dgunbufferedread(2)      DG/UX 4.30       dgunbufferedread(2)



     NAME
          dg_unbuffered_read - Synchronously read data blocks from a
          file without system buffering

     SYNOPSIS
          int   dg_unbuffered_read  (fildes, buffer, start_block, num_blocks)
             int             fildes;
             char            buffer[];
             unsigned        start_block;
             unsigned        num_blocks;

     PARAMETERS
          fildes
               A valid descriptor.

          buffer
               User data buffer.

          start_block
               Starting logical block number.

          num_blocks
               Size (in blocks) of the read.

     DESCRIPTION
          The dgunbufferedread system call transfers num_blocks
          blocks of data from the file associated with fildes into the
          buffer pointed to by buffer.  The starting block number of
          the transfer is given by the start_block parameter.

          The file position attribute of fildes is ignored by this
          interface.  The starting block position of the read must be
          specified in the call.  The file position attribute of
          fildes remains unchanged by the execution of this call.

          If mandatory record locking is enabled for the file, this
          call will fail.

     ACCESS CONTROL
          The fildes must have been opened for unbuffered I/O with the
          O_DG_UNBUFFERED flag, and fildes must also have been opened
          for read access.

     RETURN VALUE
          0..num_blocks
               Completed successfully.  The number of blocks actually
               read is returned.  The value 0 indicates EOF (end-of-
               file).

          -1   An error occurred.  Errno is set to indicate the error.

     EXCEPTIONS



     Licensed material--property of copyright holder(s)         Page 1

     dgunbufferedread(2)      DG/UX 4.30       dgunbufferedread(2)



          Errno may be set to one of the following error codes:

          EBADF
               fildes is not opened for unbuffered reading.

          EFAULT
               Buffer points outside the allocated address space.

          EINTR
               A signal was caught during the system call.

     SEE ALSO
          open(2), dg_unbuffered_write(2).










































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