writev (3)

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 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

       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  fol-
       lowing 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 read-
              ing or writing could not be done immediately.

       library; the results will be undefined and probably not what you  want.

SEE ALSO

       read(2), write(2)

GNU                               1993-04-25                          readv(3)