add doclear support

Signed-off-by: Doug Davis <dug@us.ibm.com>

demoscript/README.md

@@ -39,6 +39,8 @@ Set this environment variable to influence things...
   Which means it might not work properly if the a command requires a previous
   command to change something in the system - that change will not be there.
 - `RETRYONFAIL` : Retry all `doit` commands that have unexcepted exit code.
+- `DOCLEAR` : Clear the screen after each `doit` so that the next step will
+  be shown at the top of the screen. Good for demos.
 
 ## Demoing
 
@@ -77,6 +79,7 @@ Options:
 - `--pausetime=xx` : when using `--untilgrep` you can exit the loop by pressing
   any key. This waits `xx` seconds for a key before running the command again.
   I usually use a sub-second value.
+- `--doclear` : Clear the screen afterwards (`--nodoclear` to disable it)
 
 Example: `doit echo hello world`
 <pre>

demoscript/demoscript

@@ -118,6 +118,7 @@ function doit() {
     local norepaint=""
     local slowoutput=""
     local showcmd=""
+    local doClear="${DOCLEAR:-}"
 
     while [[ "$1" == "--"* ]]; do
         opt="$1"
@@ -137,6 +138,8 @@ function doit() {
             --norepaint   ) norepaint="1"   ;;
             --slowoutput  ) slowoutput="1"  ;;
             --showcmd*    ) showcmd="${opt#*=}" ;;
+            --doclear     ) doClear="1"     ;;
+            --nodoclear   ) doClear=""     ;;
         esac
     done
 
@@ -303,6 +306,12 @@ function doit() {
     break
 
   done
+
+  if [[ -n "$doClear" ]]; then
+    echo -n $bold"$"$normal" "
+    pause
+    clear
+  fi
 }
 
 function background() {