I just came across this when searching for the same, but I solved it myself! Assuming the command is processed with Windows / DOS, a simpler solution is to change your command to:
7z.exe -o some_dir x some_archive.7z > nul
That is, direct the output to a null file rather than the screen.
Or you could pipe the output to the DOS “find” command to only output specific data, that is,
7z.exe -o some_dir x some_archive.7z | FIND "ing archive"
This would just result in the following output.
Creating archive some_archive.7z
or
Updating archive some_archive.7z**
My final solution was to change the command to
... some_archive.7z | FIND /V "ing "
Note double space after ‘ing’. This resulted in the following output.
7-Zip 9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18
Scanning
Updating some_archive.7z
Everything is Ok
This removes the individual file processing, but produces a summary of the overall operation, regardless of the operation type.