What does question mark mean in regular expression?
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Beside this, how do you match a question mark in regex?
But if you want to search a question mark, you need to “escape” the regex interpretation of the question mark. You accomplish this by putting a backslash just before the quesetion mark, like this: ? If you want to match the period character, escape it by adding a backslash before it.
Additionally, what is Backreference in regular expression? A backreference in a regular expression identifies a previously matched group and looks for exactly the same text again. A simple example of the use of backreferences is when you wish to look for adjacent, repeated words in some text. The first part of the match could use a pattern that extracts a single word.
Additionally, what is the difference between and * in regex?
represents any single character (usually excluding the newline character), while * is a quantifier meaning zero or more of the preceding regex atom (character or group). ? is a quantifier meaning zero or one instances of the preceding atom, or (in regex variants that support it) a modifier that sets the quantifier
What does ?= Mean in regex?
= is a positive lookahead, a type of zero-width assertion. What it's saying is that the captured match must be followed by whatever is within the parentheses but that part isn't captured. Your example means the match needs to be followed by zero or more characters and then a digit (but again that part isn't captured).