Securing AI-Generated Bash Scripts Before You Run Them

Bash is the easiest language for AI to write and the easiest language to get devastating output from. A 20-line script that "just cleans up old files" can recursively delete a home directory because the model assumed a variable would always be set. A "simple log shipper" can write your secrets to a remote server because the model used set -x for debugging and forgot to remove it. I have run AI-generated bash that I should not have. Most engineers I know have too. After enough close calls, there's a short checklist that catches the worst of it. This is that checklist. The five things to check before running any AI-generated bash 1. Does it start with a strict pragma? The first lines of any non-trivial bash script should be: #!/usr/bin/env bash set -euo pipefail IFS = $' \n\t ' What each does: set -e — exit on any command failure. Without this, a failure in line 5 doesn't stop the script from happily running lines 6-50. set -u — error on undefined variables. This is the one that saves you from rm -rf $UNDEFINED/ . set -o pipefail — propagate failures through pipes. Without it, failing-command | grep something succeeds because grep succeeds. IFS=$'\n\t' — sane field splitting. Defends against word-splitting bugs in filenames. If the AI-generated script doesn't have these, add them and re-read the script. You'll often discover bugs the pragma now flags. 2. Is every variable expansion quoted? # Wrong rm -rf $TARGET_DIR # Right rm -rf " $TARGET_DIR " The wrong version is what causes the "I deleted the root directory" stories. If $TARGET_DIR is empty or contains a space, the command becomes rm -rf (delete current directory) or rm -rf foo bar (delete two unintended things). Models default to the wrong version about half the time because the right version is harder to write in chat ("escape the quotes!") and the wrong version is what most blogs show. Fix: When reading AI bash, mentally check every $VAR for quotes. Add them if missing. This is the single biggest source of bas