I've been dealing with this issue for years and finally tracked it down a few minutes ago. This is caused by the line:
declare -A _xspecs around line 1909 of /usr/share/bash-completion/bash_completion this line *should* read: declare -Ag _xspecs to ensure the _xspecs variable remains in the global scope, regardless of where bash_completion is sourced from. This has been fixed in the upstream repository for over a year: https://github.com/wpalmer/bash- completion/commit/a47bd375bb0f95dc6d388d4097c420bddb72ae33 This also causes errors in which _xspecs, having not been seen to be previously-declared, is treated as a non-associative array, resulting in errors when strings are erroneously treated as arithmetic operations to return an integer (ie: 'invalid arithmetic operator (error token is ".sh")' when trying to complete a command with .sh in the name) This issue has already been fixed, Ubuntu needs to either sync with upstream, or to apply the patch found at the above link. In the meantime, the attached patch can be used as a quick workaround -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to bash in Ubuntu. https://bugs.launchpad.net/bugs/1813090 Title: bash completions in /usr/share/bash-completion generate unbound variable errors Status in bash package in Ubuntu: New Status in bash-completion package in Ubuntu: New Bug description: After upgrading from Ubuntu 18.04 LTS to 18.04.1 LTS, I get errors whenever I attempt to tab-complete anything from an interactive bash prompt. Tab-completing nothing gives me: -bash: _xspecs[$cmd]: unbound variable Tab-completing an existing filename gives me: -bash: !ref: unbound variable I've partially narrowed down the cause to me putting `set -o nounset` in my `.bashrc` file, and something in `/usr/share/bash-completion` is triggering these unbound variable errors. (That is, the errors go away if I remove `set -o nounset` or if I make `/usr/share/bash- completion/bash_completion` exit immediately.) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/bash/+bug/1813090/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp