Conditionals

Core Idea

Conditionals make scripts choose based on a command result or test result.

Command Result

if curl -fsS https://example.org >/dev/null; then
  printf 'up\n'
else
  printf 'down\n'
fi

The branch depends on exit status: 0 succeeds, nonzero fails.

Test Result

if [[ -e "$path" ]]; then
  printf 'exists\n'
fi

Use [[ ]] for Bash tests on files, strings, and numbers.

Done When

You can predict which branch runs before executing the script.

Docs Pointers

• Read if, [[ ]], control flow, quoting, and one-liners.