added multifile document for linux things

docs/interesting_commands.md

@@ -2,8 +2,7 @@
 This file documents potentially handy commands and tools to look at or simply remember their existence.
 
 ## Take a look at
-* [ ] fzf
-* [x] tmux --> very good
+* fzf
 
 ## Remember
-* [ ] envsubst
+* envsubst

docs/linux.md

@@ -0,0 +1,5 @@
+# Linux
+
+This document collects knowledge, tips and tricks on all things Linux, that don't get their own document.
+
+- [Linux commands](linux/commands.md)

docs/linux/commands.md

@@ -0,0 +1,13 @@
+# Linux commands
+
+- [Linux commands](#linux-commands)
+  - [combine commands with *xargs*](#combine-commands-with-xargs)
+
+## combine commands with *xargs*
+
+Some commands (e.g. `chmod`) can't handle input via pipe and require the input as arguments. `xargs` takes the standard input as list of arguments seperated by spaces or newlines and executes the given command with the input parsed to a list of arguments.
+
+Usage:
+```bash
+find . -type f | xargs chmod 644
+```