Added usage, encapsulated sync error message.

- If invalid command, display: start, stop, write.

- Created isSafe to display an error message and bail if the hdd log
  directory doesn't exist.

- Split out customizable parameters.

log2ram

@@ -1,15 +1,22 @@
 #!/bin/sh
 
+SIZE=40M
+USE_RSYNC=true
+
+# don't touch anything below here.
+
 HDD_LOG=/var/log.hdd/
 RAM_LOG=/var/log/
 LOG2RAM_LOG="${HDD_LOG}log2ram.log"
-SIZE=40M
-USE_RSYNC=false
 LOG_OUTPUT="tee -a $LOG2RAM_LOG"
 
-syncToDisk () {
+isSafe () {
     [ -d $HDD_LOG ] || echo "ERROR: $HDD_LOG doesn't exist!  Can't sync."
     [ -d $HDD_LOG ] || exit 1
+}
+
+syncToDisk () {
+    isSafe
 
     if [ "$USE_RSYNC" = true ]; then
         rsync -aXWv --delete --exclude log2ram.log --links $RAM_LOG $HDD_LOG 2>&1 | $LOG_OUTPUT
@@ -19,8 +26,7 @@ syncToDisk () {
 }
 
 syncFromDisk () {
-    [ -d $HDD_LOG ] || echo "ERROR: $HDD_LOG doesn't exist!  Can't sync."
-    [ -d $HDD_LOG ] || exit 1
+    isSafe
 
     if [ "$USE_RSYNC" = true ]; then
         rsync -aXWv --delete --exclude log2ram.log --links $HDD_LOG $RAM_LOG 2>&1 | $LOG_OUTPUT
@@ -49,4 +55,8 @@ case "$1" in
   write)
       syncToDisk
       ;;
+  *)
+      echo "Usage: log2ram {start|stop|write}" >&2
+      exit 1
+      ;;
 esac