Differences

This shows you the differences between two versions of the page.

--- cheat_sheets_regex [2022/09/25 14:12] – [Groups and Ranges] gman
+++ cheat_sheets_regex [2023/02/11 14:34] (current) – [Groups and Ranges] gman
@@ Line 5: / Line 5: @@
 [[https://cheatography.com/davechild/cheat-sheets/regular-expressions/|Good Cheat Sheet]] | [[https://medium.com/factory-mind/regex-tutorial-a-simple-cheatsheet-by-examples-649dc1c3f285|Basic Explanation]]
-----
 ===== Anchors =====
 ^  Syntax  ^ Description                                             ^
@@ Line 50: / Line 48: @@
 |  [A-Q]       | Upper case letter from A to Q      |
 |  [0-7]       | Digit from 0 to 7                  |
+Use a group to "capture and replace".
+  * ''a(bc)'' parentheses create a capturing group with value ''bc''
+  * The parentheses are used to create "groups," which then get assigned a base-1 index, accessible in a //replace// with a ''$'' (i.e., the first parentheses-bounded (characters) become a group that can be referenced by ''$1'', the second group would be ''$2'', the third ''$3'', etc.).
+  * NOTE: in **gedit** you reference with a backslash: ''\'' not a ''$'' (i.e., ''\1\2\3'', etc.).
+  * See the follow table regarding **string replacements**.
+----
+===== String Replacement =====
+^  Syntax      ^ Description           ^
+|  $n  | nth non-passive group         |
+|  $2  | %%"xyz" in /^(abc(xyz))$/%%   |
+|  $1  | %%"xyz" in /^(?:abc)(xyz)$/%% |
+|  $`  | Before matched string         |
+|  $'  | After matched string          |
+|  $+  | Last matched string           |
+|  $&  | Entire matched string         |
+**Note:** Some regex implementations use \ instead of $.
+----
+===== Character Classes =====
+^  Syntax  ^ Description   ^
+|  \c  | Control character |
+|  \s  | White space       |
+|  \S  | Not white space   |
+|  \d  | Digit             |
+|  \D  | Not digit         |
+|  \w  | Word              |
+|  \W  | Not word          |
+|  \x  | Hexadecimal digit |
+|  \O  | Octal digit       |
+----
+===== POSIX =====
+^  Syntax      ^ Description                    ^
+|  [:upper:]   | Upper case letters             |
+|  [:lower:]   | Lower case letters             |
+|  [:alpha:]   | All letters                    |
+|  [:alnum:]   | Digits and letters             |
+|  [:digit:]   | Digits                         |
+|  [:xdigit:]  | Hexadecimal digits             |
+|  [:punct:]   | Punctuation                    |
+|  [:blank:]   | Space and tab                  |
+|  [:space:]   | Blank characters               |
+|  [:cntrl:]   | Control characters             |
+|  [:graph:]   | Printed characters             |
+|  [:print:]   | Printed characters and spaces  |
+|  [:word:]    | Digits, letters and underscore |
 ----