Do not allow -a and -s to be specified at the same time.
@@ -3,7 +3,11 @@
du \- display disk usage statistics
.SH SYNOPSIS
.B du
.RB [ \-a ]
.RB [ \-a
.RB |
.B \-s
.RB ]
.RB [ \-k ]
.RI [ file ...]
.SH DESCRIPTION
The note is not visible to the blocked user.