DevOps · Flashcard
Why is [[ ... ]] generally preferred over [ ... ] in Bash scripts?
- A[[ is a shell keyword that avoids word-splitting and globbing of unquoted variables
- B[[ is an external program that runs measurably faster than the builtin [ command
- C[[ automatically converts its string operands to numbers before comparing them
- D[[ is the only construct able to test whether a file exists on the disk
Why this is the answer
[[ ]] is a Bash keyword, so the shell parses it specially: unquoted variables are not word-split or glob-expanded, and it adds ==/=~ pattern matching. Option two is backwards — [ is the command-like builtin and neither is external. Option three is false — comparison stays string unless you use -eq. Option four is false — both forms support -f/-d.
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