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NAME

       readv, writev - read or write data into multiple buffers

SYNOPSIS

       #include <sys/uio.h>

       int readv(int filedes, const struct iovec *vector,
                 size_t count);

       int writev(int filedes, const struct iovec *vector,
                 size_t count);

DESCRIPTION

       The  readv()  function reads count blocks from the file associated 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 iovec {
              void *iov_base;   /* 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 VALUE

       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 undefined and probably not what you  want.

SEE ALSO

       read(2), write(2)