3 SC2199

Joachim Ansorg edited this page 2021-11-12 19:48:02 +01:00

Table of Contents

• Arrays implicitly concatenate in [[ ]]. Use a loop (or explicit * instead of @).
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:

Arrays implicitly concatenate in [[ ]]. Use a loop (or explicit * instead of @).

Problematic code:

ext=png
allowedExt=(jpg bmp png)
[[ "$ext" = "${allowedExt[@]}" ]] && echo "Extension is valid"

Correct code:

ext=png
allowedExt=(jpg bmp png)
for value in "${allowedExt[@]}"
do
  [[ "$ext" = "$value" ]] && echo "Extension is valid"
done

Rationale:

Array expansions in [[ .. ]] will implicitly concatenate into a single string, much like in assignments. The problematic code is equivalent to [ "$ext" = "jpg bmp png" ].

Instead, use a for loop to iterate over values, and apply your condition to each.

Alternatively, if you do want to concatenate all the values in the array into a single string for your test, use "$*" or "${array[*]}" to make this explicit.

Exceptions:

None.

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