readv(2)                   DG/UX 4.30                    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;

     PARAMETERS
          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 {
          caddr_t  iov_base;
          int      iov_len;
          };

          <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



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     readv(2)                   DG/UX 4.30                    readv(2)



                         <iovent> extents given in <iov[]>.


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

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


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


          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
          The related manual sections:  creat(2), dup(2), dup2(2),
          fcntl(2), ioctl(2), open(2), pipe(2), read(2), select(2),
          socket(2), socketpair(2),
          termio(7).















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