Lessons · Regex · word boundaries
The edge of a word
\b matches the position between a word character and a non-word one; \bcat\b is the whole word cat.
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What it is for
Find-and-replace of a variable name without touching names that contain it.
How to think about it
Whole word, or anywhere? Whole-word matches: \b on both sides. Remember digits and underscore are word characters too.
Worked example
pattern: \bis\bBoundary, the word, boundary.
text: this is itMatches the middle 'is', not the one inside 'this'.
Your turn
Whole word 'log'.
log
Test a pattern against real text
The trap
\b next to punctuation: 'cat.' still has a boundary after t, because . is non-word.
Practise word boundaries on HoneA question on it now, a coding challenge where there is one, and it is remembered for review. Free, no email needed.