NAME    [Toc]    [Back]

       readv, writev - read or write data into multiple buffers

SYNOPSIS    [Toc]    [Back]

       #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    [Toc]    [Back]

       The  readv()  function reads count blocks from the file associated with
       the file descriptor filedes into the multiple buffers described by vec-
       tor.

       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],  ...  vec-
       tor[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    [Toc]    [Back]

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

ERRORS    [Toc]    [Back]

       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    [Toc]    [Back]

       unknown

BUGS    [Toc]    [Back]

       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    [Toc]    [Back]

       read(2), write(2)



GNU				  1993-04-25			      READV(3)