How to code a spinner for waiting processes in a Batch file?

This can actually be done quite easily with pure native commands, you just have to know how to use the more tricky of them. No use of external tools like VBScript or nasty side effects like clearing the screen are necessary.

What you’re looking for is the equivalent of the bash “echo -n” command which outputs a line without the newline. In XP batch, this is achieved by using “set /p” (ask user for response with a prompt) with empty input as follows:

<nul (set /p junk=Hello)
echo. again.

will output the string “Hello again.” with no intervening newline.

That trick (and the use of CTRL-H, the backspace character can be seen in the following test script which starts (one after the other) a 10-second sub-task with a 20-second timeout and a 15-second sub-task with a 10-second timeout.

The payload script is created by the actual running script and its only requirement is that it do the work it has to do then delete a flag file when finished, so that the monitor function will be able to detect it.

Keep in mind that the ^H strings in this script are actually CTRL-H characters, the ^| is two separate characters used to escape the pipe symbol.

@echo off

:: Localise environment.
setlocal enableextensions enabledelayedexpansion

:: Specify directories. Your current working directory is used
:: to create temporary files tmp_*.*
set wkdir=%~dp0%
set wkdir=%wkdir:~0,-1%

:: First pass, 10-second task with 20-second timeout.
del "%wkdir%\tmp_*.*" 2>nul
echo >>"%wkdir%\tmp_payload.cmd" ping 127.0.0.1 -n 11 ^>nul
echo >>"%wkdir%\tmp_payload.cmd" del "%wkdir%\tmp_payload.flg"
call :monitor "%wkdir%\tmp_payload.cmd" "%wkdir%\tmp_payload.flg" 20

:: Second pass, 15-second task with 10-second timeout.
del "%wkdir%\tmp_*.*" 2>nul:
echo >>"%wkdir%\tmp_payload.cmd" ping 127.0.0.1 -n 16 ^>nul
echo >>"%wkdir%\tmp_payload.cmd" del "%wkdir%\tmp_payload.flg"
call :monitor "%wkdir%\tmp_payload.cmd" "%wkdir%\tmp_payload.flg" 10

goto :final

:monitor
    :: Create flag file and start the payload minimized.
    echo >>%2 dummy
    start /min cmd.exe /c "%1"

    :: Start monitoring.
    ::    i is the indicator (0=|,1=/,2=-,3=\).
    ::    m is the number of seconds left before timeout.
    set i=0
    set m=%3
    <nul (set /p z=Waiting for child to finish: ^|)

    :: Loop here awaiting completion.
    :loop
        :: Wait one second.
        ping 127.0.0.1 -n 2 >nul

        :: Update counters and output progress indicator.
        set /a "i = i + 1"
        set /a "m = m - 1"
        if %i% equ 4 set i=0
        if %i% equ 0 <nul (set /p z=^H^|)
        if %i% equ 1 <nul (set /p z=^H/)
        if %i% equ 2 <nul (set /p z=^H-)
        if %i% equ 3 <nul (set /p z=^H\)

        :: End conditions, complete or timeout.
        if not exist %2 (
            echo.
            echo.   Complete.
            goto :final
        )
        if %m% leq 0 (
            echo.
            echo.   *** ERROR: Timed-out waiting for child.
            goto :final
        )
        goto :loop
:final
endlocal