Baslinux mailing list

[sindi keesan <keesan AT sdf.lonestar.org>]

> > Steven, do you have any idea what this output of strace
> > has to do with the segmentation fault?
>
> Nope.
>
> > What is readv?
>
> Haven't clue.

NAME

   readv, writev - read or write a vector

SYNOPSIS

   #include <[42]sys/uio.h>

   ssize_t readv(int fd, const struct iovec *vector, int count);
   ssize_t writev(int fd, const struct iovec *vector, int count);

struct iovec {
    void *iov_base;    /* Starting address */
    size_t iov_len;    /* Length in bytes  */
};



DESCRIPTION

   readv  reads  data from file descriptor fd, and puts the result in the
   buffers  described  by  vector.  The number of buffers is specified by
   count.  The  buffers  are filled in the order specified. Operates just
   like  read  except  that data is put in vector instead of a contiguous
   buffer.

   writev  writes  data  to  file  descriptor  fd,  and  from the buffers
   described  by vector. The number of buffers is specified by count. The
   buffers  are  used  in  the  order specified. Operates just like write
   except that data is taken from vector instead of a contiguous buffer.


RETURN VALUE

   On  success  readv returns the number of bytes read. On success writev
   returns  the  number  of  bytes written. On error, -1 is returned, and
   errno is set appropriately.


ERRORS

   EINVAL
          An  invalid  argument  was  given.  For instance count might be
          greater  than  MAX_IOVEC, or zero. fd could also be attached to
          an  object  which  is  unsuitable  for  reading  (for readv) or
          writing (for writev).
   EFAULT
          "Segmentation  fault."  Most  likely  vector  or  some  of  the
          iov_base  pointers  points  to  memory  that  is  not  properly
          allocated.


What does the above mean?



   EBADF
          The file descriptor fd is not valid.
   EINTR
          The  call  was  interrupted  by  a  signal  before any data was
          read/written.
   EAGAIN
          Non-blocking I/O has been selected using O_NONBLOCK and no data
          was  immediately available for reading. (Or the file descriptor
          fd is for an object that is locked.)
   EISDIR
          fd refers to a directory.
   EOPNOTSUPP
          fd  refers  to  a  socket  or  device  that  does  not  support
          reading/writing.
   ENOMEM
          Insufficient kernel memory was available.

   Other errors may occur, depending on the object connected to fd.

CONFORMING TO

   4.4BSD  (the  readv  and  writev functions first appeared in BSD 4.2),
   Unix98. Linux libc5 used size_t as the type of the count parameter.

SEE ALSO

   [43]read(2), [44]write(2), [45]fprintf(3), [46]fscanf(3)

References

   2. http://linux.about.com/library/cmd/blcmdl2_readv.htm