DESCRIPTION

     The readv() function reads count blocks from the file  asso-
     ciated  with  the  file descriptor filedes into the multiple
     buffers described by vector.

     The writev() function writes at most count blocks  described
     by  vector  to  the file associated with the file descriptor
     filedes.

     The pointer vector points  to  a  struct  iovec  defined  in
     <sys/uio.h> as

          struct iovect
          {
              void *iovbase; /* Starting address  */
              size_t iov_len;    /* Number of bytes */
          } ;

     Buffers are processed in the order vector[0], vector[1], ...
     vector[count].

     The readv() function works just  like  read(2)  except  that
     multiple buffers are filled.

     The writev() function works just like write(2)  except  that
     multiple buffers are written out.

RETURN VALUES

     The readv() function returns the number of bytes  or  -1  on
     error;  the  writev()  function  returns the number of bytes
     written.

ERRORS

     The readv() and writev() functions can fail and set errno to
     the following values:

     EBADF
          fd is not a valid file descriptor.

     EINVAL
          fd is unsuitable for reading (for readv())  or  writing
          (for writev()).

     EFAULT
          buf is outside the processes' address space.

     EAGAIN
          Non-blocking I/O had been selected in the open()  call,
          and reading or writing could not be done immediately.

     EINTR
          Reading or writing was interrupted before any data  was
          transferred.

CONFORMING TO

     unknown

BUGS

     It is not advisable to mix calls to functions  like  readv()
     or  writev(),  which  operate  on file descriptors, with the
     functions from the stdio library; the results will be  unde-
     fined and probably not what you want.

SEE ALSO

     read(2), write(2)