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Characters with special meaning

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We have seen that, we are using *, +, ., $, etc for different purposes. Now, if we want to match them themselves, we have to escape them using escape character(backslash-\) .

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Below is the table for these kind of characters and their escaped version, along with their usages.

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
CharacterUsageEscaped version
\escape character\\
.predefined character class\.
|OR operator\\
*as quantifier\*
+as quantifier\+
?as quantifier\?
^boundary matcher\^
$boundary matcher\$
{in quantifier notation\{
}in quantifier notation\}
[in character class notation\[
]in character class notation\]
(in group notation\(
)in group notation\)
-range operatorNA
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Sometimes, it is also preferred to use escaped forward slash(/).

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Bonus Problems

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    +

  1. Predict the output of the following regex:

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    RegEx: \b(0|(1(01*0)*1))*\b
    + Text: This RegEx denotes the set of binary numbers divisible by 3: + 0,11,1010, 1100, 1111, 1001

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    Answer:

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    + +
    2. + +

  2. Find a regular expression to match whole lines in the text containing either Apple, Orange, Grape as a word.

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    Hint: Use ^ and $ to match whole lines.

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    Answer: ^.*\b(apple|orange|grape)\b.*$

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    3. + +

  3. Find an expression which matches cat., 896., ?=++ but not abc1.

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    Answer: ...\W

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    4. +
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