digraphs: mkdigraphs-vim: usage help if given arguments

diff --git a/tools/mkdigraphs-vim b/tools/mkdigraphs-vim
index a4bdfe803e8e636ac7d99da5d9c06464c32f3a86..b9ab42668896fa77eea51b844da490e904282025 100755 (executable)
--- a/tools/mkdigraphs-vim
+++ b/tools/mkdigraphs-vim
@@ -2,6 +2,13 @@
 
 VERSION=1.01
 
+if [ "$#" -ne 0 ]
+then
+       echo "Usage: $0 >digraphs-vim.inc.pl"
+       echo 'Collect digraph data from vim, standard output as Perl hash.'
+       exit 64 # EX_USAGE
+fi
+
 vim -e -c'echo version' -cdigraphs -cq | perl -CSD -nE '
        if ($. == 1) { # head
                say "# digraphs list from vim version ", s/\s*\z//r;