banner(1) without arguments works fine, so denote it as such in the manual.
Index: src/usr.bin/banner/banner.1 =================================================================== RCS file: /cvs/src/usr.bin/banner/banner.1,v retrieving revision 1.8 diff -u -p -r1.8 banner.1 --- src/usr.bin/banner/banner.1 6 Aug 2007 19:16:06 -0000 1.8 +++ src/usr.bin/banner/banner.1 23 Sep 2015 23:40:36 -0000 @@ -24,7 +24,7 @@ .Nd print strings in large letters .Sh SYNOPSIS .Nm banner -.Ar string ... +.Op Ar string ... .Sh DESCRIPTION .Nm prints up to 10 characters of each
