readv(2)                         DG/UX 5.4.2                        readv(2)


NAME
       readv - read from file

SYNOPSIS
       #include <sys/types.h>
       #include <sys/uio.h>

       int    readv (fildes, iov, iovent)
       int    fildes;
       struct iovec iov[];
       int    iovent;

   where:
       fildes    An active, valid file descriptor

       iov       An array of extents

       iovent    The number of extents given

DESCRIPTION
       Readv transfers data from the object associated with fildes into the
       iovent buffers specified by the members of iov[]: iov[0], iov[1],
       ..., iov[iovent-1].  Each iov[] member specifies the base address and
       length of an area in memory where data should be placed.  Readv fills
       an area completely before proceeding to the next.

       The iov structure is defined as:
              struct iovec {
              caddrt  iovbase;
              int      iovlen;
              };

       Iovent must be a positive number less than or equal to a system-
       imposed limit guaranteed to be at least MAXIOVCNT.  The length of
       each extent (iov_len) in iov[] must be non-negative and the sum of
       these lengths must not overflow a `long'.

       Except for the disposition of the data, readv is equivalent to read.

ACCESS CONTROL
       Fildes must be open for reading.

RETURN VALUE
       0..nbyte  Completed successfully.  The number of bytes actually read
                 is returned.  The value 0 indicates the `end-of-file'
                 condition.  Here, nbyte is the sum of the lengths of the
                 iovent extents given in iov[].

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

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

       EBADF     Fildes is not a valid file descriptor open for reading.



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

readv(2)                         DG/UX 5.4.2                        readv(2)


       EAGAIN    O_NDELAY is set on the I/O channel and there is a mandatory
                 lock on the file owned by a different process.

       EAGAIN    A read was attempted on an empty pipe that another process
                 has open for writing.

       EAGAIN    A read was attempted on an I/O channel that had O_NDELAY
                 set, but there was no data ready to be read at the time of
                 the call.

       EFAULT    Iov points outside the allocated address space.

       EFAULT    One or more of the iov[] members point outside the
                 allocated address space.

       EINTR     A signal was caught during the system call.

       EINVAL    Iovent was invalid.

       EINVAL    One or more of the iov_len values in iov[] was negative.

       EINVAL    The sum of the iov_len values in iov[] overflowed a `long'.

SEE ALSO
       creat(2), dup(2), dup2(2), fcntl(2), ioctl(2), open(2), pipe(2),
       read(2), select(2), socket(2), socketpair(2), termio(7).































Licensed material--property of copyright holder(s)                         2