Thank you for your bug report. I can reproduce your issue on Ubuntu 12.04 (gzip: 1.4-1ubuntu2). This is an upstream bug, therefore it would be great if you could forward the bug to the developers. As far as I can see, they are not using a bug tracker but a mailing list: https://lists.gnu.org/mailman/listinfo/bug-gzip
Note that a workaround exists: Both
zgrep -C 10 17 file.txt.gz
and
zgrep --context=10 17 file.txt.gz
give the expected result.
Thank you for your bug report. I can reproduce your issue on Ubuntu 12.04 (gzip: 1.4-1ubuntu2). This is an upstream bug, therefore it would be great if you could forward the bug to the developers. As far as I can see, they are not using a bug tracker but a mailing list: https:/ /lists. gnu.org/ mailman/ listinfo/ bug-gzip
Note that a workaround exists: Both
zgrep -C 10 17 file.txt.gz
and
zgrep --context=10 17 file.txt.gz
give the expected result.