df(1): Add --si as an alias for -H

Reviewed by:	cem (earlier version), emaste
Approved by:	emaste (mentor)
Differential Revision:	https://reviews.freebsd.org/D11749

bin/df/df.1

@@ -29,7 +29,7 @@
 .\"     @(#)df.1	8.3 (Berkeley) 5/8/95
 .\" $FreeBSD$
 .\"
-.Dd December 1, 2015
+.Dd August 8, 2017
 .Dt DF 1
 .Os
 .Sh NAME
@@ -97,7 +97,7 @@ output.
 Use unit suffixes: Byte, Kibibyte, Mebibyte, Gibibyte, Tebibyte and
 Pebibyte (based on powers of 1024) in order to reduce the number of
 digits to four or fewer.
-.It Fl H
+.It Fl H , Fl Fl si
 .Dq Human-readable
 output.
 Use unit suffixes: Byte, Kilobyte, Megabyte,

bin/df/df.c

@@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$");
 #include <ufs/ufs/ufsmount.h>
 #endif
 #include <err.h>
+#include <getopt.h>
 #include <libutil.h>
 #include <locale.h>
 #ifdef MOUNT_CHAR_DEVS
@@ -107,6 +108,12 @@ static int	thousands;
 static struct	ufs_args mdev;
 #endif
 
+static const struct option long_options[] =
+{
+	{ "si", no_argument, NULL, 'H' },
+	{ NULL, no_argument, NULL, 0 },
+};
+
 int
 main(int argc, char *argv[])
 {
@@ -142,7 +149,8 @@ main(int argc, char *argv[])
 	if (argc < 0)
 		exit(1);
 
-	while ((ch = getopt(argc, argv, "abcgHhiklmnPt:T,")) != -1)
+	while ((ch = getopt_long(argc, argv, "+abcgHhiklmnPt:T,", long_options,
+	    NULL)) != -1)
 		switch (ch) {
 		case 'a':
 			aflag = 1;