I have given an answer to “Parallel execution of shell processes” once, quoted here:
Sounds more like you want to use
Powershell 2. However, you can spawn
new cmd windows (or other processes)
by using start, see also this
answer. Although you probably have to
use some other tools and a little
trickery to create something like a
"process pool" (to have only a maximum
of n instances running at a time).
You could achieve the latter by using
tasklist /im and counting how many
are already there (for loop or wc,
if applicable) and simply wait (ping
-n 2 ::1 >nul 2>&1) and re-check again whether you can spawn a new
process.
I have cobbled together a little test
batch for this:
@echo off
for /l %%i in (1,1,20) do call :loop %%i
goto :eof
:loop
call :checkinstances
if %INSTANCES% LSS 5 (
rem just a dummy program that waits instead of doing useful stuff
rem but suffices for now
echo Starting processing instance for %1
start /min wait.exe 5 sec
goto :eof
)
rem wait a second, can be adjusted with -w (-n 2 because the first ping
returns immediately;
rem otherwise just use an address that's unused and -n 1)
echo Waiting for instances to close ...
ping -n 2 ::1 >nul 2>&1
rem jump back to see whether we can spawn a new process now
goto loop
goto :eof
:checkinstances
rem this could probably be done better. But INSTANCES should contain
the number of running instances
afterwards.
for /f "usebackq" %%t in (tasklist /fo csv /fi "imagename eq
wait.exe"^|wc -l) do set
INSTANCES=%%t
goto :eof
It spawns a maximum of four new
processes that execute in parallel and
minimized. Wait time needs to be
adjusted probably, depending on how
much each process does and how long it
is running. You probably also need to
adjust the process name for which
tasklist is looking if you're doing
something else.
There is no way to properly count the
processes that are spawned by this
batch, though. One way would be to
create a random number at the start of
the batch (%RANDOM%) and create a
helper batch that does the processing
(or spawns the processing program) but
which can set its window title to a
parameter:
@echo off
title %1
"%2" "%3"
This would be a simple batch that sets
its title to the first parameter and
then runs the second parameter with
the third as argument. You can then
filter in tasklist by selecting only
processes with the specified window
title (tasklist /fi "windowtitle eq
..."). This should work fairly
reliable and prevents too many false
positives. Searching for cmd.exe
would be a bad idea if you still have
some instances running, as that limits
your pool of worker processes.
You can use %NUMBER_OF_PROCESSORS%
to create a sensible default of how
many instances to spawn.
You can also easily adapt this to use
psexec to spawn the processes
remotely (but wouldn't be very viable
as you have to have admin privileges
on the other machine as well as
provide the password in the batch).
You would have to use process names
for filtering then, though.