adding two more commands to the second command line tutorial and adding roudh outline to advanced command line tuts

Author: matyikriszta

command-line/advanced-command-line/tutorial.md

@@ -5,3 +5,8 @@ title: Advanced command line
 
 flags
 wildcards
+piping and redirection
+sort?
+uniq?
+grep
+sed aka stream editor

command-line/command-line/tutorial.md

@@ -48,4 +48,22 @@ rm -r command?
 
 ### `rmdir` or removing directoris (only works on empty directories)
 
-to delete folders with files in them use rm -r command
+to delete folders with files in them use rm -r command
+
+### `cat` or printing? streaming? files
+
+```bash
+$ cat file.txt
+```
+
+```bash
+$ cat file.txt > other_file.txt
+```
+
+redirecting and rewriting
+
+```bash
+$ cat file.txt >> other_file.txt
+```
+
+redirecting and appending