⚠️ Scripts WITHOUT Shebang Do NOT Work with command_not_found_handle ⚠️

The problem: without shebang handle does NOT work (fails to stop)

If you are relying on command_not_found_handle in your scripts. Make sure you are properly adding Shebang Hashbang to your scripts.

For example if you run the following example (without shebang):

main() {
  echo "START-[\$\$=$$/$BASHPID]"
  iDontExist
  sleep 0.5
  echo "FINISH-[\$\$=$$/$BASHPID]"
}

main "${@}"

You could be quite surprised to find out the following output, which shows that command_not_found_handle did trigger, BUT somehow the FINISH echo was allowed to execute:

START-[$$=2706051/2706051]
    🤷 [$$=2706051/2706052] command_not_found_handle: invoked with arguments=['iDontExist'].
    🤷 [$$=2706051/2706052] command_not_found_handle: Interrupting process group [2706051].
    🤷 FunctionChain: [main:7 (scratch.sh)-->main:3 (scratch.sh)-->command_not_found_handle]
FINISH-[$$=2706051/2706051]

The fix: Add shebang

The fix is simple, add #!/usr/bin/env bash and it works as expected:

#!/usr/bin/env bash

main() {
  echo "START-[\$\$=$$/$BASHPID]"
  iDontExist
  sleep 0.5
  echo "FINISH-[\$\$=$$/$BASHPID]"
}

main "${@}"

START-[$$=2707408/2707408]
    🤷 [$$=2707408/2707409] command_not_found_handle: invoked with arguments=['iDontExist'].
    🤷 [$$=2707408/2707409] command_not_found_handle: Interrupting process group [2707408].
    🤷 FunctionChain: [main:10 (scratch.sh)-->main:5 (scratch.sh)-->command_not_found_handle]

Why it doesn't work.

At the time of writing I do not know why. Asking claude 4.5 sonnet gave some hallucination answers that were not correct.

• command_not_found_handle