I confirm this in bash 3.2-5ubuntu1 on 9.04, and that it's still present in bash 4.0-5ubuntu2 on 9.10.
It only triggers for the commands with special completion processing. For example:
cd /tmp
cp /bin/cat cat
./cat<space><space>foo (tab between spaces triggers error "-bash: $index: substring expression < 0")
cp /bin/cat test
./test<space><space>foo (tab between spaces does NOT trigger an error)
I confirm this in bash 3.2-5ubuntu1 on 9.04, and that it's still present in bash 4.0-5ubuntu2 on 9.10. <space> foo (tab between spaces triggers error "-bash: $index: substring expression < 0") space>< space>foo (tab between spaces does NOT trigger an error)
It only triggers for the commands with special completion processing. For example:
cd /tmp
cp /bin/cat cat
./cat<space>
cp /bin/cat test
./test<