Question

write regular expressions including modifiers, operators, and metacharacters​

Answer 1

Answer:

Answer is given. In explanation part

Explanation:

Regular expression patterns are often used with modifiers (also called flags) that redefine regex behavior. Regex modifiers can be regular (e.g. /abc/i ) and inline (or embedded) (e.g. (? i)abc ). The most common modifiers are global, case-insensitive, multiline and dotall modifiers.

You compose regular expressions from operators. In the following sections, we describe the regular expression operators specified by POSIX; GNU also uses these. Most operators have more than one representation as characters. See section Regular Expression Syntax, for what characters represent what operators under what circumstances.

For most operators that can be represented in two ways, one representation is a single character and the other is that character preceded by `\'. For example, either `(' or `\(' represents the open-group operator. Which one does depends on the setting of a syntax bit, in this case RE_NO_BK_PARENS. Why is this so? Historical reasons dictate some of the varying representations, while POSIX dictates others.

A metacharacter is a character that has a special meaning during pattern processing. You use metacharacters in regular expressions to define the search criteria and any text manipulations. Search string metacharacters are different from replacement string metacharacters.