Improving Batch File for loop with start subcommand

Question

I\'ve currently got a very simple script which pings 10 IPs:

@ECHO OFF
for /L %%i in (100, 1, 110) DO (
  START /W /B cmd /c ping -n 1 192.168.0.%%i | find \         


        

Answer 1

Seems that I have found a pure batch-file solution. Basically, the script fires several ping commands simultaneously, which all write their result to individual log files; these files are monitored for write-access, because the files are write-locked as long as the respective ping processes are ongoing; as soon as write-access is granted, the first lines of the log files containing the IP addresses are copied into a summary log file. So here is the code -- see all the explanatory rem remarks:

@echo off
setlocal EnableExtensions DisableDelayedExpansion

rem // Predefine IP addresses as an array:
for /L %%J in (0,1,5) do (
    set "IP[%%J]=127.0.0.%%J"
)

rem // Ping IP addresses simultaneously, create individual log files:
for /F "tokens=2,* delims=[=]" %%J in ('set IP[') do (
    start "" /B cmd /C ping -n 2 %%K ^| find "TTL=" ^> "%~dpn0_%%J.log"
)

rem // Deplete summary log file:
> "%~dpn0.log" rem/

rem /* Polling loop to check whether individual log files are accessible;
rem    this works, because a pinging process is not yet finished, the
rem    respective log file is still opened and therefore write-locked: */
:POLL
rem // Give processor some time:
> nul timeout /T 1 /NOBREAK
rem /* Loop through all available array elements; for every accomplished
rem    pinging process, the related array element becomes deleted, so
rem    finally, there should not be any more array elements defined: */
for /F "tokens=2 delims=[=]" %%J in ('2^> nul set IP[') do (
    rem // Suppress error message in case log file is write-locked:
    2> nul (
        rem // Try to append nothing to the log file:
        >> "%~dpn0_%%J.log" rem/ && (
            rem /* Appending succeeded, hence log file is no longer locked
            rem    and the respective pinging process has been finished;
            rem    therefore read the first line containing the IP: */
            set "FILE=" & set "IP="
            < "%~dpn0_%%J.log" set /P IP=""
            rem // Copy the read line to the summary log file:
            if defined IP >> "%~dpn0.log" call echo(%%IP%%
            rem // Undefine related array element:
            set "IP[%%J]="
            rem // Store log file path for later deletion:
            set "FILE=%~dpn0_%%J.log"
        )
        rem // Delete individual log file finally:
        if defined FILE call del "%%FILE%%"
    )
)
rem // Jump to polling loop in case there are still array elements:
> nul 2>&1 set IP[ && goto :POLL

endlocal
exit /B