file.tell() -- obscure IOError

[Skip Montanaro]

    Uwe> when does tell() raise an IOError?

When the underlying ftell() call returns -1 for the position, that is, an
error was detected.  My ftell man page suggests the only possible error
condition that ftell detects directly is

       EBADF  The stream specified is not a seekable stream.

however it also says

       The  function  fgetpos, fseek, fsetpos, and ftell may also
       fail and set errno for any of the errors specified for the
       routines fflush(3), fstat(2), lseek(2), and malloc(3).

-- 
Skip Montanaro
skip at pobox.com
consulting: http://manatee.mojam.com/~skip/resume.html