+--- a/zgrep.1 2012-09-10 03:20:56.541637782 +0300
++++ b/zgrep.1 2012-09-10 03:18:21.000000000 +0300
+@@ -11,7 +11,13 @@ zgrep \- search possibly compressed file
+ invokes
+ .I grep
+ on compressed or gzipped files.
+-All options specified are passed directly to
++These
++.I grep
++options will cause
++.I zgrep
++to terminate with an error code:
++.BI (-[drRzZ] | --di* | --exc* | --inc* | --rec* | --nu*) .
++All other options specified are passed directly to
+ .IR grep .
+ If no file is specified, then the standard input is decompressed
+ if necessary and fed to grep.
+@@ -23,6 +29,8 @@ If the GREP environment variable is set,
+ uses it as the
+ .I grep
+ program to be invoked.
++.SH EXIT CODE
++2 - An option that is not supported was specified.
+ .SH AUTHOR
+ Charles Levert (charles@comm.polymtl.ca)
+ .SH "SEE ALSO"