Ok, I understand the issue... The posix exec family of functions assume
that the first value in the argument list is the command to execute
itself. Therefore, for a command like "sort -nr" execvp in the popen2
posix function should have called execvp with "sort" for the command and
"sort -nr" for the argument list.. The attached patch fixes this and a
couple of other things like a spurious error when killing the child
process when the execvp fails...
I do however see a number of defunct child processes, but that is no
different from the old popen2 function.. I think this patch is good to go..