Regular Expression to Match a Line that Doesn’t Contain a Word

To create a regular expression that matches a line that does not contain a specific word, you can use a negative lookahead. A negative lookahead asserts that a pattern is not followed by another pattern.

Here’s the regular expression:

Regular Expression:

Explanation:

1. ^: Asserts the position at the start of the line.
2. (?!.*\bword\b): This is the negative lookahead. It asserts that, starting from the beginning of the line, the word word is not present anywhere in the line. The .* matches any number of characters, and \b ensures the word boundaries so it doesn’t match part of a larger word.
3. .*: This matches the rest of the line after the negative lookahead.

Example:

• For a line that does not contain the word “apple”:
  • Matches: “This is a test.”, “Bananas are yellow.”
  • Does not match: “I like apple pie.”, “An apple a day keeps the doctor away.”

How It Works:

• The expression checks if the word “apple” appears anywhere on the line using the negative lookahead (?!.*\bapple\b).
• If “apple” is not present, it will match the whole line .*.