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 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 undefined  and  probably  not
       what you want.

SEE ALSO

       read(2), write(2)