Is it me or lldb for mac os x (replacing gdb) does not allow you to pipe a file into the stdin, to be used by the process being debugged?
reading the instructions there
(lldb) process launch -i <file>
Should do the trick. Note you can't say:
(lldb) run -i <file>
since run
is an alias for process launch --
so all its arguments are passed to the process being launched.
There's a general "help" facility that can show you more about all the lldb commands.
(lldb) help process launch
would have shown you this option.