Steps to Reproduce: Run `zgrep PATTERN *.gz' in sufficiently big directory and press C-C. zgrep runs on. The press C-\. zgrep says somtehing like `/usr/bin/zgrep: line 99: 24010 Done $compressor -cdfq "$i" 24011 Quit | if test $files_with_matches -eq 1; then' and still goes on.
Fixed in gzip-1.3.5-alt3.