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Contrary to [[[ prevents word splitting of variable values. So, if VAR="var with spaces", you do not need to double quote $VAR in a test – even though using quotes remains a good habit. Also, [[ prevents pathname expansion, so literal strings with wildcards do not try to expand to filenames. Using [[== and != interpret strings to the right as shell glob patterns to be matched against the value to the left, for instance: [[ "value" == val* ]].

Reference: here