Index: usr.bin/uniq/uniq.1
===================================================================
--- usr.bin/uniq/uniq.1
+++ usr.bin/uniq/uniq.1
@@ -31,7 +31,7 @@
 .\"     From: @(#)uniq.1	8.1 (Berkeley) 6/6/93
 .\" $FreeBSD$
 .\"
-.Dd May 1, 2018
+.Dd November 6, 2019
 .Dt UNIQ 1
 .Os
 .Sh NAME
@@ -39,8 +39,7 @@
 .Nd report or filter out repeated lines in a file
 .Sh SYNOPSIS
 .Nm
-.Op Fl c
-.Op Fl d | Fl u
+.Op Fl c | Fl d | Fl D | Fl u
 .Op Fl i
 .Op Fl f Ar num
 .Op Fl s Ar chars
@@ -75,7 +74,24 @@
 Precede each output line with the count of the number of times the line
 occurred in the input, followed by a single space.
 .It Fl d , Fl -repeated
-Only output lines that are repeated in the input.
+Output a single copy of each line that is repeated in the input.
+.It Fl D , Fl -all-repeated Op Ar septype
+Output all lines that are repeated (like
+.Fl d ,
+but each copy of the repeated line is written).
+The optional
+.Ar septype
+argument controls how to separate groups of repeated lines in the output;
+it must be one of the following values:
+.Pp
+.Bl -tag -compact -width separate
+.It none
+Do not separate groups of lines (this is the default).
+.It prepend
+Output an empty line before each group of lines.
+.It separate
+Output an empty line after each group of lines.
+.El
 .It Fl f Ar num , Fl -skip-fields Ar num
 Ignore the first
 .Ar num
Index: usr.bin/uniq/uniq.c
===================================================================
--- usr.bin/uniq/uniq.c
+++ usr.bin/uniq/uniq.c
@@ -65,11 +65,18 @@
 #include <wchar.h>
 #include <wctype.h>
 
-static int cflag, dflag, uflag, iflag;
+static int Dflag, cflag, dflag, uflag, iflag;
 static int numchars, numfields, repeats;
 
+/* Dflag values */
+#define	DF_NONE		0
+#define	DF_NOSEP	1
+#define	DF_PRESEP	2
+#define	DF_POSTSEP	3
+
 static const struct option long_opts[] =
 {
+	{"all-repeated",optional_argument,	NULL, 'D'},
 	{"count",	no_argument,		NULL, 'c'},
 	{"repeated",	no_argument,		NULL, 'd'},
 	{"skip-fields",	required_argument,	NULL, 'f'},
@@ -101,9 +108,19 @@
 	(void) setlocale(LC_ALL, "");
 
 	obsolete(argv);
-	while ((ch = getopt_long(argc, argv, "+cdif:s:u", long_opts,
+	while ((ch = getopt_long(argc, argv, "+D::cdif:s:u", long_opts,
 	    NULL)) != -1)
 		switch (ch) {
+		case 'D':
+			if (optarg == NULL || strcasecmp(optarg, "none") == 0)
+				Dflag = DF_NOSEP;
+			else if (strcasecmp(optarg, "prepend") == 0)
+				Dflag = DF_PRESEP;
+			else if (strcasecmp(optarg, "separate") == 0)
+				Dflag = DF_POSTSEP;
+			else
+				usage();
+			break;
 		case 'c':
 			cflag = 1;
 			break;
@@ -194,7 +211,10 @@
 
 		if (comp) {
 			/* If different, print; set previous to new value. */
-			show(ofp, prevline);
+			if (Dflag == DF_POSTSEP && repeats > 0)
+				fputc('\n', ofp);
+			if (!Dflag)
+				show(ofp, prevline);
 			p = prevline;
 			b1 = prevbuflen;
 			prevline = thisline;
@@ -206,12 +226,22 @@
 			thisbuflen = b1;
 			tthis = NULL;
 			repeats = 0;
-		} else
+		} else {
+			if (Dflag) {
+				if (repeats == 0) {
+					if (Dflag == DF_PRESEP)
+						fputc('\n', ofp);
+					show(ofp, prevline);
+				}
+				show(ofp, thisline);
+			}
 			++repeats;
+		}
 	}
 	if (ferror(ifp))
 		err(1, "%s", ifn);
-	show(ofp, prevline);
+	if (!Dflag)
+		show(ofp, prevline);
 	exit(0);
 }
 
@@ -276,7 +306,7 @@
 show(FILE *ofp, const char *str)
 {
 
-	if ((dflag && repeats == 0) || (uflag && repeats > 0))
+	if ((!Dflag && dflag && repeats == 0) || (uflag && repeats > 0))
 		return;
 	if (cflag)
 		(void)fprintf(ofp, "%4d %s", repeats + 1, str);
@@ -343,6 +373,6 @@
 usage(void)
 {
 	(void)fprintf(stderr,
-"usage: uniq [-c] [-d | -u] [-i] [-f fields] [-s chars] [input [output]]\n");
+"usage: uniq [-c | -d | -D | -u] [-i] [-f fields] [-s chars] [input [output]]\n");
 	exit(1);
 }