Implement this (quoted from the updated man page): If the first token

of a rule specification is a single dash (``-''), rules are read from
the standard input and the rest of the specification is ignored.

sbin/devfs/devfs.8

@@ -143,6 +143,10 @@ and the actions determine what should be done when a rule matches a node.
 For example, a rule can be written that sets the GID to
 .Li games
 for all devices with major number 53.
+If the first token of a rule specification is a single dash
+.Pq Dq - ,
+rules are read from the standard input and the rest of the specification
+is ignored.
 .Pp
 The following conditions are recognized.
 Conditions are ANDed together when matching a device;
@@ -311,6 +315,28 @@ will be applied to all nodes.
 Since hiding all nodes isn't very useful, we can undo like so:
 .Pp
 .Dl devfs rule apply unhide
+.Pp
+which applies
+.Cm unhide
+to all the nodes,
+causing them to reappear.
+.Pp
+.Dl cat my_rules | devfs rule -s 10 add -
+.Pp
+Add all the rules from the file
+.Pa my_rules
+to ruleset 10.
+.Pp
+.Dl devfs rule -s 20 show | devfs rule -s 10 add -
+.Pp
+Since
+.Cm show
+outputs valid rules,
+this feature can be used to copy rulesets.
+The above copies all the rules from ruleset 20 into ruleset 10.
+The rule numbers are preserved,
+but ruleset 10 may already have rules with non-conflicting numbers
+(these will be preserved).
 .Sh SEE ALSO
 .Xr jail 2 ,
 .Xr glob 3 ,

sbin/devfs/devfs.c

@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2002 Dima Dorfman.
+ * Copyright (c) 2001, 2002 Dima Dorfman.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -32,7 +32,9 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/queue.h>
 
+#include <assert.h>
 #include <err.h>
 #include <fcntl.h>
 #include <paths.h>
@@ -131,6 +133,93 @@ eatonum(const char *s)
 	return (num);
 }	
 
+/*
+ * Read a line from a /FILE/.  If the return value isn't 0, it is the
+ * length of the line, a pointer to which exists in /line/.  It is the
+ * caller's responsibility to free(3) it.  If the return value is 0,
+ * there was an error or we reached EOF, and /line/ is undefined (so,
+ * obviously, the caller shouldn't try to free(3) it).
+ */
+size_t
+efgetln(FILE *fp, char **line)
+{
+	size_t rv;
+	char *cp;
+
+	cp = fgetln(fp, &rv);
+	if (cp == NULL) {
+		*line = NULL;
+		return (rv);
+	}
+	if (cp[rv - 1] == '\n') {
+		cp[rv - 1] = '\0';
+		*line = strdup(cp);
+		if (*line == NULL)
+			errx(1, "cannot allocate memory");
+		--rv;
+	} else {
+		*line = malloc(rv + 1);
+		if (*line == NULL)
+			errx(1, "cannot allocate memory");
+		memcpy(*line, cp, rv);
+		*line[rv] = '\0';
+	}
+	assert(rv == strlen(*line));
+	return (rv);
+}
+
+struct ptrstq {
+	STAILQ_ENTRY(ptrstq)	 tq;
+	void			*ptr;
+};
+
+/*
+ * Create an argument vector from /line/.  The caller must free(3)
+ * /avp/, and /avp[0]/ when the argument vector is no longer
+ * needed unless /acp/ is 0, in which case /avp/ is undefined.
+ * /avp/ is NULL-terminated, so it is actually one longer than /acp/.
+ */
+void
+tokenize(const char *line, int *acp, char ***avp)
+{
+	static const char *delims = " \t\n";
+	struct ptrstq *pt;
+	STAILQ_HEAD(, ptrstq) plist;
+	char **ap, *cp, *wline, *xcp;
+
+	line += strspn(line, delims);
+	wline = strdup(line);
+	if (wline == NULL)
+		errx(1, "cannot allocate memory");
+
+	STAILQ_INIT(&plist);
+	for (xcp = wline, *acp = 0;
+	     (cp = strsep(&xcp, delims)) != NULL;)
+		if (*cp != '\0') {
+			pt = calloc(1, sizeof(*pt));
+			if (pt == NULL)
+				errx(1, "cannot allocate memory");
+			pt->ptr = cp;
+			STAILQ_INSERT_TAIL(&plist, pt, tq);
+			++*acp;
+		}
+	if (*acp == 0)
+		return;
+	assert(STAILQ_FIRST(&plist)->ptr == wline);
+	*avp = malloc(sizeof(**avp) * (*acp + 1));
+	if (*avp == NULL)
+		errx(1, "cannot allocate memory");
+	for (ap = *avp; !STAILQ_EMPTY(&plist);) {
+		pt = STAILQ_FIRST(&plist);
+		*ap = pt->ptr;
+		++ap;
+		assert(ap <= *avp + (*acp));
+		STAILQ_REMOVE_HEAD(&plist, tq);
+		free(pt);
+	}
+	*ap = NULL;
+}
+
 void
 usage(void)
 {

sbin/devfs/extern.h

@@ -48,6 +48,8 @@ command_t rule_main, ruleset_main;
 int atonum(const char *, uint16_t *);
 int eatoi(const char *);
 uint16_t eatonum(const char *);
+size_t efgetln(FILE *, char **);
+void tokenize(const char *, int *, char ***);
 void usage(void) __dead2;
 
 extern int mpfd;		/* Mount-point file descriptor. */

sbin/devfs/rule.c

@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/conf.h>
 #include <sys/ioctl.h>
 
+#include <assert.h>
 #include <err.h>
 #include <errno.h>
 #include <grp.h>
@@ -46,6 +47,9 @@ __FBSDID("$FreeBSD$");
 
 #include "extern.h"
 
+static void rulespec_infp(FILE *fp, int cmd, devfs_rsnum rsnum);
+static void rulespec_instr(struct devfs_rule *dr, const char *str,
+    devfs_rsnum rsnum);
 static void rulespec_intok(struct devfs_rule *dr, int ac, char **av,
     devfs_rsnum rsnum);
 static void rulespec_outfp(FILE *fp, struct devfs_rule *dr);
@@ -109,10 +113,14 @@ rule_add(int ac, char **av)
 
 	if (ac < 2)
 		usage();
-	rulespec_intok(&dr, ac - 1, av + 1, in_rsnum);
-	rv = ioctl(mpfd, DEVFSIO_RADD, &dr);
-	if (rv == -1)
-		err(1, "ioctl DEVFSIO_RADD");
+	if (strcmp(av[1], "-") == 0)
+		rulespec_infp(stdin, DEVFSIO_RADD, in_rsnum);
+	else {
+		rulespec_intok(&dr, ac - 1, av + 1, in_rsnum);
+		rv = ioctl(mpfd, DEVFSIO_RADD, &dr);
+		if (rv == -1)
+			err(1, "ioctl DEVFSIO_RADD");
+	}
 	return (0);
 }
 
@@ -127,10 +135,14 @@ rule_apply(int ac __unused, char **av __unused)
 	if (ac < 2)
 		usage();
 	if (!atonum(av[1], &rnum)) {
-		rulespec_intok(&dr, ac - 1, av + 1, in_rsnum);
-		rv = ioctl(mpfd, DEVFSIO_RAPPLY, &dr);
-		if (rv == -1)
-			err(1, "ioctl DEVFSIO_RAPPLY");
+		if (strcmp(av[1], "-") == 0)
+			rulespec_infp(stdin, DEVFSIO_RAPPLY, in_rsnum);
+		else {
+			rulespec_intok(&dr, ac - 1, av + 1, in_rsnum);
+			rv = ioctl(mpfd, DEVFSIO_RAPPLY, &dr);
+			if (rv == -1)
+				err(1, "ioctl DEVFSIO_RAPPLY");
+		}
 	} else {
 		rid = mkrid(in_rsnum, rnum);
 		rv = ioctl(mpfd, DEVFSIO_RAPPLYID, &rid);
@@ -248,6 +260,49 @@ ruleset_main(int ac, char **av)
 }
 
 
+/*
+ * Input rules from a file (probably the standard input).  This
+ * differs from the other rulespec_in*() routines in that it also
+ * calls ioctl() for the rules, since it is impractical (and not very
+ * useful) to return a list (or array) of rules, just so the caller
+ * can call call ioctl() for each of them.
+ */
+static void
+rulespec_infp(FILE *fp, int cmd, devfs_rsnum rsnum)
+{
+	struct devfs_rule dr;
+	char *line;
+	int rv;
+
+	assert(fp == stdin);	/* XXX: De-hardcode "stdin" from error msg. */
+	while (efgetln(fp, &line)) {
+		rulespec_instr(&dr, line, rsnum);
+		rv = ioctl(mpfd, cmd, &dr);
+		if (rv == -1)
+			err(1, "ioctl");
+		free(line);	/* efgetln() always malloc()s. */
+	}
+	if (ferror(stdin))
+		err(1, "stdin");
+}
+
+/*
+ * Construct a /struct devfs_rule/ from a string.
+ */
+static void
+rulespec_instr(struct devfs_rule *dr, const char *str, devfs_rsnum rsnum)
+{
+	char **av;
+	int ac;
+
+	tokenize(str, &ac, &av);
+	if (ac == 0)
+		errx(1, "unexpected end of rulespec");
+	rulespec_intok(dr, ac, av, rsnum);
+	free(av[0]);
+	free(av);
+}
+
 /*
  * Construct a /struct devfs_rule/ from ac and av.
  */