Hypershadow in regular expression

When using regular expressions, be sure to consider the behavior of various characters in it. In this case, let's explore how to deal with hyphens.

question:

How to modify existing pattern [a-zA-Z0-9!$*\t\r\n] to include hyphen matches?

Answer:

Understand the hyphen in regular expressions

Usually, hyphen acts as a normal character in a regular expression. However, their behavior changes slightly when they appear in the character class [] and have other characters before and after them. In these specific cases, they have special uses.

Match hyphen

To match hyphen, you can choose the following options:

• directly use hyphen: The hyphen in the character class - represents itself.
• Escape hyphen: You can also use \- to escape hyphen, although this is not required.

Example

Consider the following scenarios:

• [-abc]: Match any instance of the characters a, b, c, or hyphen.
• [-abc]: equivalent to [-abc].
• [ab\-c]: Match a, b, c or hyphen. Pay attention to the position of escape hyphen.
• [ab-d]: Specifies the range from a to d, excluding hyphens. Here the hyphen is interpreted as a range indicator.