Introduction-to-Using-the-Command-Line.md

@@ -2,6 +2,7 @@
 1. [What is the Command Line](#what-is-the-command-line)
 1. [Why use the Command Line](#why-use-the-command-line)
     1. [Resize images example](#resize-images-example)
+    1. [MagicMirror timed menu display example](#magicmirror-timed-menu-display-example)
     1. [Roon timed zone playback example](#roon-timed-zone-playback-example)
 1. [History](#history)
 1. [Opening the Command Line](#opening-the-command-line)
@@ -111,6 +112,59 @@ done
 echo "Successfully resized ${count} JPEG images in ${IMGDIR}"
 ```
 
+### MagicMirror timed menu display example
+Another example of command line automation, specific to the MirrorCommandLine
+project, might be display of a menu on a restaurant bathroom mirror that has
+been setup as a MagicMirror. The restaurant owner wants the bathroom mirror to
+display the breakfast menu during morning hours, the lunch menu at midday, and
+the dinner menu in the evening. Before and after business hours she just wants
+the mirror to be a mirror.
+
+This can be accomplished by a worker manually configuring the MagicMirror in each
+of the bathrooms but again is prone to error, delays, and can be tedious. Let's
+do it in the command line utilizing the Cron facility which enables commands to
+be executed at specified times of day, specified days/weeks/months/years, and so on.
+
+After installing the MirrorCommandLine package and configuring MagicMirror config
+files for each of the menus to be displayed, a Cron job can be created that executes
+the appropriate `mirror` command at the desired time of day on the desired days
+of the week. The Crontab entries might look like:
+
+```bash
+# This is a file named menucrontab.in with cron job entries
+# m h  dom mon dow   command
+#
+# Breakfast starts at 7am on weekdays
+0 7 * * 1-5 /usr/local/bin/mirror breakfast
+# Lunch starts at 11am on weekdays
+0 11 * * 1-5 /usr/local/bin/mirror lunch
+# Dinner starts at 4pm on weekdays
+0 16 * * 1-5 /usr/local/bin/mirror dinner
+# Closing time is 9pm on weekdays
+0 21 * * 1-5 /usr/local/bin/mirror blank
+# Breakfast starts at 8am on weekends
+0 8 * * 0,6 /usr/local/bin/mirror breakfast
+# Lunch starts at 1pm on weekends
+0 13 * * 0,6 /usr/local/bin/mirror lunch
+# Dinner starts at 5pm on weekends
+0 17 * * 0,6 /usr/local/bin/mirror dinner
+# Closing time is 11pm on weekends
+0 23 * * 0,6 /usr/local/bin/mirror blank
+```
+Create the above crontab file and, on each of the MagicMirror systems in
+the restaurant setup the cron job by executing, as the user with MagicMirror
+administration privileges, the command:
+
+`crontab menucrontab.in`
+
+Verify the cron jobs are setup properly with:
+
+`crontab -l`
+
+No 4 times daily tasks prone to error need be performed. Changing the
+menu or the schedule of menu display will be a one-time task performed in a
+few minutes by the MagicMirror administrator.
+
 ### Roon timed zone playback example
 There are many many uses of the command line in automation. Another example,
 specific to the RoonCommandLine project, might be the playback of specified
@@ -157,7 +211,7 @@ Verify the cron jobs are setup properly with:
 
 `crontab -l`
 
-Viola! No daily tasks prone to error need be performed in order to have
+No daily tasks prone to error need be performed in order to have
 automated zone specific playlists start and stop at designated times of day.
 Changing the playlist or the schedule of playback will be a one-time task
 performed in a few minutes by the Roon administrator.