-bb (Set output log level) switch

The switch sets output log level for Delete/Add/Update/Extract operations.

-bb[0-3]

Log level	Description
-bb0	disable log (default).
-bb1 or -bb	show names of processed files in log.
-bb2	show names of additional files that were processed internally in solid archives: skipped files for "Extract" operation, repacked files for "Add" / "Update" operations.
-bb3	show information about additional operations (Analyze, Replicate) for "Add" / "Update" operations.

7z a a.7z *.txt -bb

adds *.txt files to a.7z archive and shows all files that were processed.

7z u a.7z *.txt -bb3

updates *.txt files in a.7z archive and shows information about additional operations.

Notes from this site

Not part of the 7-Zip manual. Written by this site; examples checked with 7-Zip 26.04.

Use 7z on Windows and 7zz (the official console binary) on Linux/macOS, with patterns quoted on Linux/macOS (omit the quotes in Windows cmd).

7zz a a.7z '*.txt' -bb1
7zz x a.7z -bb
7zz t a.7z -bb
7zz u s.7z folder -bb2
7zz a a.7z '*.txt' -bb1 -bso1 -bsp0 > log.txt

The last line writes the list of processed files to log.txt without percent progress. See -bs for the stream switches. Sample output of line 1:

+ a.txt
+ b.txt

Files read from disk: 2
Archive size: 169 bytes (1 KiB)
Everything is Ok

Extraction prints - a.txt and testing prints T a.txt in the same way.

-bb alone is the same as -bb1. In 7-Zip 26.04, adding, extracting and testing print no file names by default; with -bb each file gets a line. Markers: + added, - extracted, T tested.
-bb2 on extraction from a solid archive also lists files that were read but not kept (marked with a dot). On update it lists repacked files (R) and updated ones (U), which shows why an update is slow.
-bb3 on update also shows files in blocks that were kept as they are (=).

-bb also works with t, although the vendor command list does not show it. With the l (List) command it changes nothing.
Only the file list goes to standard output. Warnings and errors go to the error stream, so a redirected log stays readable and problems still show on the console.