docs: update

README.md

@@ -10,6 +10,7 @@ A collection of pure POSIX `sh` alternatives to external processes
 * [STRINGS](#strings)
     * [Strip pattern from start of string](#strip-pattern-from-start-of-string)
     * [Strip pattern from end of string](#strip-pattern-from-end-of-string)
+    * [Trim all white-space from string and truncate spaces](#trim-all-white-space-from-string-and-truncate-spaces)
 
 <!-- vim-markdown-toc -->
 
@@ -51,3 +52,33 @@ rstrip() {
 $ rstrip "The Quick Brown Fox" " Fox"
 The Quick Brown
 ```
+
+## Trim all white-space from string and truncate spaces
+
+This is an alternative to `sed`, `awk`, `perl` and other tools. The
+function below works by abusing word splitting to create a new string
+without leading/trailing white-space and with truncated spaces.
+
+**Example Function:**
+
+```sh
+# shellcheck disable=SC2086,SC2048
+trim_all() {
+    # Usage: trim_all "   example   string    "
+    set -f
+    set -- $*
+    printf '%s\n' "$*"
+    set +f
+}
+```
+
+**Example Usage:**
+
+```shell
+$ trim_all "    Hello,    World    "
+Hello, World
+
+$ name="   John   Black  is     my    name.    "
+$ trim_all "$name"
+John Black is my name.
+```