Improve filesystem example. Demonstrates unusual append mode for littlefs

vickash · vickash · commit 5e60669b8a7f · 2023-07-09T16:48:18.000-04:00
diff --git a/main/examples/filesystem.rb b/main/examples/filesystem.rb
@@ -1,12 +1,34 @@
-# Wait a bit for startup to complete.
-ESP32::System.delay(500)
+# Get the number of previous boots from a file.
+boot_count = nil
+File.open('/storage/boot_count.txt', 'a+') { |f| boot_count = f.gets }
 
-string1 = "testing "
-string2 = "1,2,3..."
+# Increment it.
+boot_count = 0 unless boot_count
+boot_count = boot_count.to_i
+boot_count += 1
 
-puts "Writing to /storage/test.txt: \"#{string1}#{string2}\""
-File.open('/storage/test.txt', 'w') { |f| f.write(string1) }
-File.open('/storage/test.txt', 'a') { |f| f.write(string2) }
+# Write new count back to file.
+File.open('/storage/boot_count.txt', 'w') { |f| f.puts(boot_count) }
 
-print "Read from /storage/text.txt: "
+# Display it.
+puts "Boot count: #{boot_count}"
+
+# If first boot, write then append to /storage/test.txt.
+if boot_count == 1
+  string1 = "testing "
+  string2 = "1,2,3..."
+  puts "Writing to /storage/test.txt: \"#{string1}#{string2}\""
+  
+  File.open('/storage/test.txt', 'w') { |f| f.write(string1) }
+  
+  # WARNING: littlefs append mode starts with the file pointer at 0 (start of file).
+  File.open('/storage/test.txt', 'a') do |f|
+    # Move file pointer to the end with #seek.
+    f.seek(0, File::SEEK_END)
+    f.write(string2)
+  end
+end
+
+# Read from /storage/test.txt on every boot.
+print "Read from /storage/test.txt: "
 File.open('/storage/test.txt', 'r') { |f| f.each_line { |l| puts l } }
