if & Test Expressions in Bash

From the Bash Scripting cheat sheet · Conditionals · verified Jul 2026

if/elif/else with [[ ]].

bash

# Quick Reference
if [[ "$x" == "yes" ]]; then
    echo "ok"
elif [[ -z "$x" ]]; then
    echo "empty"
else
    echo "no"
fi

💡 Use [[ ]] (bash) over [ ] (POSIX test) - it handles empty vars, &&, and patterns safely.

⚡ == does glob-pattern matching in [[ ]]; =~ does regex matching.

📌 String tests: == != -z (empty) -n (non-empty). Numeric: -eq -ne -lt -gt -le -ge.

🟢 cmd && success || failure is a compact if/else, but beware if success itself can fail.

conditionalstest

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