I've whipped up a quick modification to ifconfig(8) to limit the
display of -a and -l to just up (using -u) or down (using -d)
interfaces, a la Solaris's ifconfig.

I think this could be useful, potentially in /etc/netstart.

Also, if stuff like "ifconfig -a <some command>" ever works, limiting
it to up or down interfaces could be a big win.

In any case, the code is rather simple; diffs attached.

Problems with committing this?

Index: ifconfig.8
===================================================================
RCS file: /cvsroot/src/sbin/ifconfig/ifconfig.8,v
retrieving revision 1.16
diff -c -r1.16 ifconfig.8
*** ifconfig.8	1997/04/10 19:10:16	1.16
--- ifconfig.8	1997/04/16 08:44:08
***************
*** 33,39 ****
  .\"
  .\"     @(#)ifconfig.8	8.4 (Berkeley) 6/1/94
  .\"
! .Dd June 1, 1994
  .Dt IFCONFIG 8
  .Os BSD 4.2
  .Sh NAME
--- 33,39 ----
  .\"
  .\"     @(#)ifconfig.8	8.4 (Berkeley) 6/1/94
  .\"
! .Dd April 16, 1997
  .Dt IFCONFIG 8
  .Os BSD 4.2
  .Sh NAME
***************
*** 54,75 ****
  .Nm ifconfig
  .Fl a
  .Op Fl m
  .Op Ar protocol_family
  .Nm ifconfig
  .Fl l
  .Sh DESCRIPTION
! .Nm Ifconfig
  is used to assign an address
  to a network interface and/or configure
  network interface parameters.
! .Nm Ifconfig
  must be used at boot time to define the network address
  of each interface present on a machine; it may also be used at
  a later time to redefine an interface's address
  or other operating parameters.
  .Pp
  Available operands for
! .Nm ifconfig:
  .Bl -tag -width Ds
  .It Ar Address
  For the
--- 54,79 ----
  .Nm ifconfig
  .Fl a
  .Op Fl m
+ .Op Fl d
+ .Op Fl u
  .Op Ar protocol_family
  .Nm ifconfig
  .Fl l
+ .Op Fl d
+ .Op Fl u
  .Sh DESCRIPTION
! .Nm
  is used to assign an address
  to a network interface and/or configure
  network interface parameters.
! .Nm
  must be used at boot time to define the network address
  of each interface present on a machine; it may also be used at
  a later time to redefine an interface's address
  or other operating parameters.
  .Pp
  Available operands for
! .Nm ifconfig :
  .Bl -tag -width Ds
  .It Ar Address
  For the
***************
*** 290,297 ****
  the hardware will be re-initialized.
  .El
  .Pp
! .Pp
! .Nm Ifconfig
  displays the current configuration for a network interface
  when no optional parameters are supplied.
  If a protocol family is specified,
--- 294,300 ----
  the hardware will be re-initialized.
  .El
  .Pp
! .Nm
  displays the current configuration for a network interface
  when no optional parameters are supplied.
  If a protocol family is specified,
***************
*** 300,318 ****
  If the
  .Fl m
  flag is passed before an interface name,
! .Nm ifconfig
  will display all of the supported media for the specified interface.
  Optionally, the
  .Fl a
  flag may be used instead of an interface name.  This flag instructs
! .Nm ifconfig
  to display information about all interfaces in the system.
  .Pp
  The
  .Fl l
  flag may be used to list all available interfaces on the system, with
  no other additional information.  Use of this flag is mutually exclusive
! with all other flags and commands.
  .Pp
  Only the super-user may modify the configuration of a network interface.
  .Sh DIAGNOSTICS
--- 303,331 ----
  If the
  .Fl m
  flag is passed before an interface name,
! .Nm
  will display all of the supported media for the specified interface.
+ .Pp
  Optionally, the
  .Fl a
  flag may be used instead of an interface name.  This flag instructs
! .Nm
  to display information about all interfaces in the system.
+ .Fl d
+ limits this to interfaces that are down, and
+ .Fl u
+ limits this to interfaces that are up.
  .Pp
  The
  .Fl l
  flag may be used to list all available interfaces on the system, with
  no other additional information.  Use of this flag is mutually exclusive
! with all other flags and commands, except for
! .Fl d
! (only list interfaces that are down)
! and
! .Fl u 
! (only list interfaces that are up).
  .Pp
  Only the super-user may modify the configuration of a network interface.
  .Sh DIAGNOSTICS
Index: ifconfig.c
===================================================================
RCS file: /cvsroot/src/sbin/ifconfig/ifconfig.c,v
retrieving revision 1.33
diff -c -r1.33 ifconfig.c
*** ifconfig.c	1997/04/10 19:10:17	1.33
--- ifconfig.c	1997/04/16 08:44:14
***************
*** 121,127 ****
  int	newaddr = 1;
  int	nsellength = 1;
  int	af;
! int	mflag, lflag;
  
  void 	notealias __P((char *, int));
  void 	notrailers __P((char *, int));
--- 121,127 ----
  int	newaddr = 1;
  int	nsellength = 1;
  int	af;
! int	mflag, lflag, dflag, uflag;
  
  void 	notealias __P((char *, int));
  void 	notrailers __P((char *, int));
***************
*** 257,268 ****
  
  	/* Parse command-line options */
  	aflag = mflag = 0;
! 	while ((ch = getopt(argc, argv, "alm")) != -1) {
  		switch (ch) {
  		case 'a':
  			aflag = 1;
  			break;
  
  		case 'l':
  			lflag = 1;
  			break;
--- 257,272 ----
  
  	/* Parse command-line options */
  	aflag = mflag = 0;
! 	while ((ch = getopt(argc, argv, "adlmu")) != -1) {
  		switch (ch) {
  		case 'a':
  			aflag = 1;
  			break;
  
+ 		case 'd':
+ 			dflag = 1;
+ 			break;
+ 
  		case 'l':
  			lflag = 1;
  			break;
***************
*** 271,276 ****
--- 275,284 ----
  			mflag = 1;
  			break;
  
+ 		case 'u':
+ 			uflag = 1;
+ 			break;
+ 
  		default:
  			usage();
  			/* NOTREACHED */
***************
*** 467,473 ****
  		err(1, "SIOCGIFCONF");
  	ifr = ifc.ifc_req;
  	ifreq.ifr_name[0] = '\0';
! 	for (i = 0, idx = 0; i < ifc.ifc_len; idx++) {
  		ifr = (struct ifreq *)((caddr_t)ifc.ifc_req + i);
  		i += sizeof(ifr->ifr_name) +
  			(ifr->ifr_addr.sa_len > sizeof(struct sockaddr)
--- 475,481 ----
  		err(1, "SIOCGIFCONF");
  	ifr = ifc.ifc_req;
  	ifreq.ifr_name[0] = '\0';
! 	for (i = 0, idx = 0; i < ifc.ifc_len; ) {
  		ifr = (struct ifreq *)((caddr_t)ifc.ifc_req + i);
  		i += sizeof(ifr->ifr_name) +
  			(ifr->ifr_addr.sa_len > sizeof(struct sockaddr)
***************
*** 481,498 ****
  		(void) strncpy(name, ifr->ifr_name, sizeof(ifr->ifr_name));
  		ifreq = *ifr;
  
  		/*
  		 * Are we just listing the interfaces?
  		 */
  		if (lflag) {
! 			if (idx)
  				putchar(' ');
! 			printf(name);
  			continue;
  		}
  
- 		if (getinfo(&ifreq) < 0)
- 			continue;
  		if (sdl == NULL) {
  			status(NULL, 0);
  		} else {
--- 489,512 ----
  		(void) strncpy(name, ifr->ifr_name, sizeof(ifr->ifr_name));
  		ifreq = *ifr;
  
+ 		if (getinfo(&ifreq) < 0)
+ 			continue;
+ 		if (dflag && (flags & IFF_UP) != 0)
+ 			continue;
+ 		if (uflag && (flags & IFF_UP) == 0)
+ 			continue;
+ 
+ 		idx++;
  		/*
  		 * Are we just listing the interfaces?
  		 */
  		if (lflag) {
! 			if (idx > 1)
  				putchar(' ');
! 			fputs(name, stdout);
  			continue;
  		}
  
  		if (sdl == NULL) {
  			status(NULL, 0);
  		} else {
***************
*** 577,583 ****
  	char *vname;
  	int value;
  {
! 	printf("Note: trailers are no longer sent, but always received\n");
  }
  
  /*ARGSUSED*/
--- 591,597 ----
  	char *vname;
  	int value;
  {
! 	puts("Note: trailers are no longer sent, but always received");
  }
  
  /*ARGSUSED*/
***************
*** 1444,1450 ****
  	sns->sns_len = sizeof(*sns);
  	sns->sns_addr = ns_addr(addr);
  	if (which == MASK)
! 		printf("Attempt to set XNS netmask will be ineffectual\n");
  }
  
  #define SISO(x) ((struct sockaddr_iso *) &(x))
--- 1458,1464 ----
  	sns->sns_len = sizeof(*sns);
  	sns->sns_addr = ns_addr(addr);
  	if (which == MASK)
! 		puts("Attempt to set XNS netmask will be ineffectual");
  }
  
  #define SISO(x) ((struct sockaddr_iso *) &(x))
***************
*** 1522,1528 ****
  		"\t[ mediaopt mopts ]\n",
  		"\t[ -mediaopt mopts ]\n",
  		"\t[ link0 | -link0 ] [ link1 | -link1 ] [ link2 | -link2 ]\n",
! 		"       ifconfig -a [ -m ] [ af ]\n",
! 		"       ifconfig -l\n");
  	exit(1);
  }
--- 1536,1542 ----
  		"\t[ mediaopt mopts ]\n",
  		"\t[ -mediaopt mopts ]\n",
  		"\t[ link0 | -link0 ] [ link1 | -link1 ] [ link2 | -link2 ]\n",
! 		"       ifconfig -a [ -m ] [ -d ] [ -u ] [ af ]\n",
! 		"       ifconfig -l [ -d ] [ -u ]\n");
  	exit(1);
  }