sleep_until: safety

.config/shell/functions/sleep-until

@@ -4,9 +4,13 @@
 
 sleep_until() {
    if [ -n "$1" ] && date --date="$*" > /dev/null 2>&1; then
-      echo "Sleeping until:  $(date --date="$*")"
-
-      sleep $(( $(date -f - +%s- <<< "$*"$'\nnow') 0 ))
+      SLEEP_TIME="$(( $(date -f - +%s- <<< "$*"$'\nnow') 0 ))"
+      if [ "$SLEEP_TIME" -gt 0 ]; then
+         echo "Sleeping until:  $(date --date="$*")  (${SLEEP_TIME}s)"
+         sleep "$SLEEP_TIME"
+      else
+         echo "Sadly, you cannot sleep to a time in the past"
+      fi
    else
       echo "Please input a date"
    fi