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--- linux:bash [2026/05/15 11:29] – [FILESYSTEM] v1ctor
+++ linux:bash [2026/05/15 13:30] (current) – [REDIRECTS vs PIPES] v1ctor
@@ Line 60: / Line 60: @@
 </code>
+To make env variable permanent, you need to store it in a file. Which file - depends on the Shell type:
+Type of Shells:
+^ Shell Type ^ When it starts ^ Example ^ Reads file ^
+| Login Shell | You authenticate (SSH, TTY login, su -, bash -l) | SSH into a server | ~/.profile |
+| Interactive non-login | You open a new terminal in an existing session | New tab in your terminal  emulator | ~/.bashrc |
+  * **~/.profile** — runs once per login session. Good for:
+    * export PATH=..., export EDITOR=vim
+  * **~/.bashrc** — runs every time you open a new interactive bash shell. Good for:
+    * aliases, shell functions, prompt
+==== REDIRECTS vs PIPES ====
+The core difference: redirects connect a stream to a file (a redirect always has a file on one side). Pipes connect one process to another process.
+Pipes: process → process:
+<code bash>
+cmd1 | cmd2           # Takes cmd1's stdout and feeds it directly into cmd2's stdin. No file involved
+ls | grep ".txt"      # ls output becomes grep's input
+</code>
+==== STANDARD INPUT and OUTPUT ====
+Unix programs have 1 input and 2 outputs.
+When you run a command from a terminal, they all go to/from the terminal by default, e.g.:
+<code bash>
+$ cat
+hello   # Stdin is connected to the terminal, you can type there.
+hello   # Stdout - cat prints it right away after you pressed enter.
+</code>
+** < redirects Stdin**
+<code bash>
+cat < foo.txt
+bar
+</code>