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--- regex:all_text_not_containing [2022/09/20 23:28] – peter
+++ regex:all_text_not_containing [2025/05/27 07:55] (current) – peter
@@ Line 16: / Line 16: @@
 ----
+===== Match strings that do not start with a sequence =====
+Ignore strings that start with the label "abc_".
+Use a negative look-ahead assertion:
+<code bash>
+^(?!abc_).+
+</code>
+Or, use a negative look-behind assertion:
+<code bash>
+(^.{1,3}$|^.{4}(?<!abc_).*)
+</code>
+Or, use plain old character sets and alternations:
+<code bash>
+^([^a]|a($|[^b]|b($|[^c]|c($|[^_])))).*
+</code>
+----
+===== Match strings that do not end in particular sequence =====
+Use a negative lookbehind assertion:
+<code bash>
+^[/\w\.-]+(?<!\.html)$
+</code>
+or, use a lookahead:
+<code bash>
+^(?!.*\.html$)[/\w\.-]+$
+</code>
+or, another use of a lookahead assertion:
+<code bash>
+/((?!\.html$)[/\w.-])+/
+</code>
+<WRAP info>
+**NOTE:**
+  * **(** - Start a group for the purposes of repeating.
+  * **(?!\.html$)** - Negative lookahead assertion for the pattern **/\.html$/**.
+  * **[/\w.-]** - The pattern for matching a URL character.
+  * **)+** - Repeat the group.
+To force it to match the entire string, anchor the entire pattern with **^** at the start and **$** at the end; otherwise it is free to only match a portion of the string. With this change, it becomes:
+<code bash>
+/^((?!\.html$)[/\w.-])+$/
+</code>
+</WRAP>
+----
+===== References =====
+https://www.regular-expressions.info/lookaround.html