Answer:
Does [\\\[] match \ ? Yes
Does it match [ ? Yes
Does [\\\[] match \ ? Yes
Does it match [ ? Yes
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Regular Expression (Delimit with quotes) |
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String (Delimit with quotes) |
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If you wanted to match any digit '0' through '9' you could use
[0123456789],
but that would be awkward.
You can specify a range of characters by the following:
Rule 3. Ranges of Characters
To show a range of characters, use square backets and separate the starting character from
the ending character with a hyphen.
For example, [0-9] matches any digit.
Several ranges can be put inside square brackets.
For example, [A-CX-Z] matches 'A' or 'B' or 'C' or 'X' or 'Y' or 'Z'.
| Regular Expression | Matches |
|---|---|
[0-9] | 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 |
[0-1][0-3] | 00, 01, 02, 03, 10, 11, 12, 13 |
[a-d] | a, b, c, d |
Chapter [1-9] | Chapter 1, Chapter 2, ... |
[cC]hapter [1-9] | chapter 1, Chapter 1, chapter 2, Chapter 2, ... |
[A-Za-z][1-9] | A9, a1, b8, W7, ... |
The character range feature follows the collating sequence of the character
set being used, usually ASCII.
[a-z] includes all lower case alphabetic characters
because those characters appear in
sequence in ASCII.
Detail: If the dash character is the first one in the list, then
it is treated as an ordinary character.
For example [-AZ] matches '-' or 'A' or 'Z' .
And tag[- ]line matches "tag-line" and "tag line"
as in a previous example.
Detail:
The characters connected by the dash must be in order.
For example, [9-0] is not valid.
Bug Alert!
[A-z] specifies all those characters
between character capital 'A' and lower case 'z' in the ASCII sequence.
This range includes several non-alphabetic characters
that lie between 'Z' and 'a' in that sequence.
Write a RE that matches any alphabetic character, upper or lower case, and nothing else. (Hint: use two ranges.)