Index: fields.c
===================================================================
RCS file: /cvs/src/usr.bin/sort/fields.c,v
retrieving revision 1.11
diff -u -r1.11 fields.c
--- fields.c	2006/02/14 14:45:36	1.11
+++ fields.c	2007/07/28 12:51:23
@@ -118,7 +118,7 @@
 		    fieldtable->flags)) == NULL)
 			return (1);
 
-	if (UNIQUE)
+	if (UNIQUE || STABLE)
 		*(keypos-1) = REC_D;
 	keybuf->offset = keypos - keybuf->data;
 	keybuf->length = keybuf->offset + line->size;
@@ -196,7 +196,7 @@
  * To avoid confusing the exponent and the mantissa, use a field delimiter
  * if the exponent is exactly 61, 61+252, etc--this is ok, since it's the
  * only time a field delimiter can come in that position.
- * Reverse order is done analagously.
+ * Reverse order is done analogously.
  */
 
 u_char *
Index: fsort.c
===================================================================
RCS file: /cvs/src/usr.bin/sort/fsort.c,v
retrieving revision 1.18
diff -u -r1.18 fsort.c
--- fsort.c	2007/03/13 17:33:58	1.18
+++ fsort.c	2007/07/28 12:51:24
@@ -173,8 +173,11 @@
 		}
 		get = getnext;
 		if (!ntfiles && !mfct) {	/* everything in memory--pop */
-			if (nelem > 1 && radixsort((const u_char **)keylist,
-			    nelem, weights, REC_D))
+			if (nelem > 1 && (STABLE ?
+			    sradixsort((const u_char **)keylist,
+			    nelem, weights, REC_D) :
+			    radixsort((const u_char **)keylist,
+			    nelem, weights, REC_D)))
 				err(2, NULL);
 			append(keylist, nelem, depth, outfp, putline, ftbl);
 			break;					/* pop */
Index: msort.c
===================================================================
RCS file: /cvs/src/usr.bin/sort/msort.c,v
retrieving revision 1.20
diff -u -r1.20 msort.c
--- msort.c	2007/03/13 17:33:58	1.20
+++ msort.c	2007/07/28 12:51:24
@@ -295,7 +295,7 @@
 	for (cwts = wts; cwts; cwts = (cwts == wts1 ? 0 : wts1)) {
 		pos1 = rec1->data;
 		pos2 = rec2->data;
-		if (!SINGL_FLD && UNIQUE)
+		if (!SINGL_FLD && UNIQUE || STABLE)
 			end = pos1 + min(rec1->offset, rec2->offset);
 		else
 			end = pos1 + min(rec1->length, rec2->length);
Index: sort.1
===================================================================
RCS file: /cvs/src/usr.bin/sort/sort.1,v
retrieving revision 1.29
diff -u -r1.29 sort.1
--- sort.1	2007/05/31 19:20:16	1.29
+++ sort.1	2007/07/28 12:51:24
@@ -136,6 +136,10 @@
 option.)
 .It Fl r
 Reverse the sense of comparisons.
+.It Fl s
+Enable stable sort. Use additional resources (see sradixsort(3)).
+.It Fl S
+Disable stable sort. This is the default. Provided for compatibility only.
 .El
 .Pp
 The treatment of field separators can be altered using these options:
Index: sort.c
===================================================================
RCS file: /cvs/src/usr.bin/sort/sort.c,v
retrieving revision 1.34
diff -u -r1.34 sort.c
--- sort.c	2007/03/13 17:33:58	1.34
+++ sort.c	2007/07/28 12:51:24
@@ -80,7 +80,7 @@
  * masks of ignored characters.  Alltable is 256 ones
  */
 u_char dtable[NBINS], itable[NBINS], alltable[NBINS];
-int SINGL_FLD = 0, SEP_FLAG = 0, UNIQUE = 0;
+int SINGL_FLD = 0, SEP_FLAG = 0, UNIQUE = 0, STABLE = 0;
 struct coldesc *clist;
 int ncols = 0;
 int ND = 10;			/* limit on number of -k options. */
@@ -125,7 +125,7 @@
 	fixit(&argc, argv);
 	if (!issetugid() && (outfile = getenv("TMPDIR")))
 		tmpdir = outfile;
-	while ((ch = getopt(argc, argv, "bcdfik:mHno:rR:t:T:uy:z")) != -1) {
+	while ((ch = getopt(argc, argv, "bcdfik:mHno:rR:t:T:uy:zsS")) != -1) {
 		switch (ch) {
 		case 'b': fldtab->flags |= BI | BT;
 			break;
@@ -192,6 +192,12 @@
 			d_mask['\n'] = d_mask[' '];
 			d_mask[REC_D] = REC_D_F;
 			break;
+		case 's':
+			STABLE = 1;
+			break;
+		case 'S':
+			STABLE = 0;
+			break;
 		case '?':
 		default:
 			usage(NULL);
@@ -340,7 +346,7 @@
 
 	if (msg != NULL)
 		warnx("%s", msg);
-	(void)fprintf(stderr, "usage: %s [-bcdfHimnruz] "
+	(void)fprintf(stderr, "usage: %s [-bcdfHimnruzsS] "
 	    "[-k field1[,field2]] [-o output] [-R char]\n"
 	    "\t[-T dir] [-t char] [file ...]\n", __progname);
 	exit(2);
Index: sort.h
===================================================================
RCS file: /cvs/src/usr.bin/sort/sort.h,v
retrieving revision 1.6
diff -u -r1.6 sort.h
--- sort.h	2003/06/03 02:56:16	1.6
+++ sort.h	2007/07/28 12:51:24
@@ -133,7 +133,7 @@
 extern u_char ascii[NBINS], Rascii[NBINS], Ftable[NBINS], RFtable[NBINS];
 extern u_char alltable[NBINS], dtable[NBINS], itable[NBINS];
 extern u_char d_mask[NBINS];
-extern int SINGL_FLD, SEP_FLAG, UNIQUE;
+extern int SINGL_FLD, SEP_FLAG, UNIQUE, STABLE;
 extern int REC_D;
 extern char *tmpdir;
 extern int ND;		/* limit on number of -k options. */