Created Terminal & script usage (markdown)

Terminal-&-script-usage.md

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+# Terminal and script usage
+
+- Each 'App' is simply a small `install` script, `uninstall` script, two icon sizes, and two text files containing the description and a website URL.
+ - Each App is stored in its own separate directory. `~/pi-apps/apps/` holds all these app directories. The Zoom app, for example, would be located at `~/pi-apps/apps/Zoom/`.
+ - Because of the contained nature of each app folder, it's really easy to 'package' your own apps: just put the folder in a ZIP file and send it to friends. (or upload it as a [new issue](https://github.com/Botspot/pi-apps/issues/new) so your app can be added to Pi-Apps)
+ - When you click Install, the selected App's `install` script is executed. (Or, in some cases, the `install-32` or `install-64` script is executed.)
+ - When you click Uninstall, the selected App's `uninstall` script is executed.
+## Terminal usage
+ - The `manage` script is similar to `apt-get` - it handles installing apps, uninstalling them, keeping them updated, and more. `Manage` does not include a GUI, but in one case, a dialog will ask if you really want to install the same app twice.
+   - To **install** an app, run this:
+`~/pi-apps/manage install Zoom`
+   - To **uninstall** an app:
+`~/pi-apps/manage uninstall Zoom`
+   - To **update** a single app:  
+`~/pi-apps/manage update Zoom`
+Note that if an app is up-to-date, no files will be moved around.
+   - To **check** all apps for updates:  
+ `~/pi-apps/manage check-all`
+ This command will return a list of updatable apps, separated by the `|` character.
+   - To **update all** apps:
+  `~/pi-apps/manage update-all`
+  Please note that this will not update the Pi-Apps main scripts! It only updates your apps and that's an important distinction.
+   - To update everything:
+   `~/pi-apps/updater`
+ - To **list** all apps:
+ `ls ~/pi-apps/apps`
+ Note that this will also list the `template` app, which is usually hidden.
+
+## App folder:
+Each app folder contains some of these files:
+ - `credits` Contains credits for the app. This file may mention who created the app originally, who compiled it, who submitted it to Pi-Apps, etc. Few apps use this file.
+ - `description` This stores the app's description. If you hover your mouse over an app in the app list, it will display a tooltip derived from the first line of this file.
+ - `icon-24.png` This is a 24x24 pixel icon that is displayed in the app list.
+ - `icon-64.png` This is a 64x64 pixel icon that is displayed in the Details page.
+ - `install` If the app installs correctly on both 32bit and 64bit, and it only needs one install script for either CPU type, one single install script is used.
+ - `install-32` This script installs an app on 32bit OS'es, and is 32bit-specific.
+ - `install-64` This script installs an app on 64bit OS'es, and is 64bit-specific.
+Sidenote: if an app only has an `install-32` script, then Pi-Apps will assume it's for 32bit OS'es only and will hide that app on 64bit installations.
+ - `uninstall` This script uninstalls the app. It must undo all changes made during install, but with one exception: **It must not permanently delete any user-generated config!** [We don't want people's Minecraft worlds being deleted during an update.](https://github.com/Botspot/pi-apps/issues/44)