chore: improved folder structure

knowledge base/chmod.md

@@ -3,18 +3,37 @@
 ## TL;DR
 
 ```sh
-# Copy permissions from another file.
-# Only available in GNU cp.
-chmod --reference 'reference-file' 'changed-file'
+# Change permissions of files or directories.
+chmod '775' "path/to/dir"
+chmod 'u=rw' "path/to/dir"
+chmod 'go+x' "path/to/file"
+
+# Set 'setuid' bit.
+chmod '04755' "path/to/dir"
+chmod 'u-s' "path/to/file"
+
+# Set 'setgid' bit.
+chmod '02775' "path/to/dir"
+chmod 'g+s' "path/to/file"
+
+# Set 'sticky' bit.
+# Allows only the *owner* to change content and delete.
+chmod '01775' "path/to/dir"
+chmod 'a+t' "path/to/file"
+
+# Set combinations of 'set*id' and 'sticky' bits.
+chmod '03775' "path/to/setgid/and/sticky/dir"
+chmod '05664' "path/to/setuid/and/sticky/file"
+chmod '07644' "path/to/setuid/setgid/and/sticky/file"
 ```
 
 ## Sources
 
-- [18 selected super-useful Linux one-liners]
+- [File permissions and attributes]
 
 <!--
   References
   -->
 
 <!-- Others -->
-[18 selected super-useful linux one-liners]: https://medium.com/codex/18-selected-super-useful-linux-one-liners-398ba6d20f8c
+[file permissions and attributes]: https://wiki.archlinux.org/title/File_permissions_and_attributes