Interview › Scripting (Bash, Groovy)
What is the difference between [ ], [[ ]], and (( )) in Bash? [Basic]
Answer
[ ] is the traditional test command, [[ ]] is Bash's safer and more capable conditional expression, and (( )) is for arithmetic evaluation. In Bash scripts, I prefer [[ ]] for strings and files, and (( )) for numeric logic.
Technical explanation
[ is a command, so it requires spaces and has more quoting pitfalls.
[[ ]] supports pattern matching, regex with =~, and safer handling of empty variables.
(( )) treats variables as numbers and is ideal for counters and numeric comparisons.
Hands-on example
file="app.log"
[[ -f "$file" && "$file" == *.log ]] && echo "log file"
count=5
if (( count > 3 )); then
echo "count is high"
fi
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