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The metacharacter \b is an anchor like the caret and the dollar sign. It matches at a position that is called a “word boundary”. This match is zero-length. There are three different positions that qualify as word boundaries: Before the first character in the string, if the first character is a word character.
End of String or Line: $ The $ anchor specifies that the preceding pattern must occur at the end of the input string, or before \n at the end of the input string. If you use $ with the RegexOptions. Multiline option, the match can also occur at the end of a line.
\\. matches the literal character . . the first backslash is interpreted as an escape character by the Emacs string reader, which combined with the second backslash, inserts a literal backslash character into the string being read. the regular expression engine receives the string \.
The Difference Between \s and \s+ For example, expression X+ matches one or more X characters. Therefore, the regular expression \s matches a single whitespace character, while \s+ will match one or more whitespace characters.
You don't give us the language, but if your regex flavour support look behind assertion, this is what you need:
.*(?<!a)$
(?<!a) is a negated lookbehind assertion that ensures, that before the end of the string (or row with m modifier), there is not the character "a".
See it here on Regexr
You can also easily extend this with other characters, since this checking for the string and isn't a character class.
.*(?<!ab)$
This would match anything that does not end with "ab", see it on Regexr
Use the not (^) symbol:
.*[^a]$
If you put the ^ symbol at the beginning of brackets, it means "everything except the things in the brackets." $ is simply an anchor to the end.
For multiple characters, just put them all in their own character set:
.*[^a][^b]$
To search for files not ending with ".tmp" we use the following regex:
^(?!.*[.]tmp$).*$
Tested with the Regex Tester gives following result:
.*[^a]$
the regex above will match strings which is not ending with a.
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