Simple shell conditional.
{{command}} && echo "success" || echo "failure"
if {{condition}}; then echo "true"; else echo "false"; fi
help test
if [[ -z $GIT_BRANCH ]]; then echo "true"; else echo "false"; fi
if [[ -e {{filename}} ]]; then echo "true"; else echo "false"; fi
if [[ ! -d {{path/to/directory}} ]]; then echo "true"; else echo "false"; fi