Something like:
#!/usr/bin/env bash
main() {
if [[ $# -eq 0 ]]; then
echo "Error: missing path to new content."
echo "Example: $0 blog/mypost.md"
exit 1
fi
declare path=$1
hugo new "${path%%/*}/$(date +%Y/%m)/${path#*/}"
}
set -euo pipefail
main "$@"