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I am trying to replace all occurrences of a whole word on emacs (say foo) using M-x replace-regexp.
The problem is that I don't want to replace occurrences of foo in underscored words such as word_foo_word
If I use \bfoo\b to match foo then it will match the underscored strings; because as I understand emacs considers underscores to be part of word boundaries, which is different to other RegEx systems such as Perl.
What would be the correct way to proceed?
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The word boundary \b matches positions where one side is a word character (usually a letter, digit or underscore—but see below for variations across engines) and the other side is not a word character (for instance, it may be the beginning of the string or a space character).
The metacharacter \b is an anchor like the caret and the dollar sign. It matches at a position that is called a “word boundary”.
A word boundary is a zero-width test between two characters. To pass the test, there must be a word character on one side, and a non-word character on the other side. It does not matter which side each character appears on, but there must be one of each.
The regexp \<foo\> or \bfoo\b matches foo only when it's not preceded or followed by a word constituent character (syntax code w, usually alphanumerics, so it matches in foo_bar but not in foo1).
Since Emacs 22, the regexp \_<foo_bar\_> matches foo_bar only when it's not preceded or followed by a symbol-constituent character. Symbol constituents include not only word constituents (alphanumerics) but also punctuation characters that are allowed in identifiers, meaning underscores in most programming languages.
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