doc: indicate that FILE arguments are optional with rm -f

* src/rm.c (usage): s/FILE/[FILE]/.
Fixes http://bugs.gnu.org/18187

1 files changed, 1 insertions, 1 deletions

diff --git a/src/rm.c b/src/rm.c
index 5baea1533..708d85d21 100644
--- a/src/rm.c
+++ b/src/rm.c
@@ -132,7 +132,7 @@ usage (int status)
     emit_try_help ();
   else
     {
-      printf (_("Usage: %s [OPTION]... FILE...\n"), program_name);
+      printf (_("Usage: %s [OPTION]... [FILE]...\n"), program_name);
       fputs (_("\
 Remove (unlink) the FILE(s).\n\
 \n\