in reply to cmd.exe piping stress
Any ideas about how to proceed with debugging,
To see what is being received from the pipe, use a one-liner to receive and redirect it:
perl units.pl COM1 < dmp4.tests > dmp4.results perl units.pl COM1 < dmp4.tests | perl -pe1 > dmp4.piped diff dmp4.results dmp4.piped
Then you can compare the two.
What are those COM1 references doing?
The comments mention warnings and errors. You are only piping/redirecting STDOUT not STDERR? Not that it should make any difference in what gets redirected or piped as STDERR would get displayed on the console in both cases--unless you are redirecting stuff internally to the program? To the serial port for example?