SC3006 – ShellCheck Wiki

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In POSIX sh, standalone ((..)) is undefined.

Problematic code:

variable=1
if ((variable)); then
  echo variable is not zero
fi

Correct code:

bash supports standalone ((..)) natively.

For POSIX compliance, use

variable=1
if [ "${variable}" != 0 ]; then
  echo variable is not zero
fi

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