Bash regex =~ operator

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  1. What is the operator =~ called?

    I’m not sure it has a name. The bash documentation just calls it the =~ operator.

  2. Is it only used to compare the right side against the left side?

    The right side is considered an extended regular expression. If the left side matches, the operator returns 0, and 1 otherwise.

  3. Why are double square brackets required when running a test?

    Because =~ is an operator of the [[ expression ]] compound command.

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