Index: env.1
===================================================================
RCS file: /cvsroot/src/usr.bin/env/env.1,v
retrieving revision 1.12
diff -u -r1.12 env.1
--- env.1	8 Jun 2007 18:20:42 -0000	1.12
+++ env.1	8 Feb 2020 10:21:01 -0000
@@ -32,7 +32,7 @@
 .\"	from: @(#)printenv.1	6.7 (Berkeley) 7/28/91
 .\"	$NetBSD: env.1,v 1.12 2007/06/08 18:20:42 wiz Exp $
 .\"
-.Dd June 8, 2007
+.Dd February 8, 2020
 .Dt ENV 1
 .Os
 .Sh NAME
@@ -41,6 +41,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl i
+.Op Fl u Ar name
 .Op Ar name=value ...
 .Oo
 .Ar utility
@@ -66,6 +67,21 @@
 to completely ignore the environment
 it inherits.
 .Pp
+The option
+.Sq Fl u Ar name
+causes removal of the
+.Ar name
+environment variable if it is in the environment.
+This is similar to the
+.Ic unset
+command in
+.Xr sh 1 .
+The value for
+.Ar name
+must not include the
+.Ql =
+character.
+.Pp
 If no
 .Ar utility
 is specified,
@@ -106,6 +122,10 @@
 The historic
 .Fl
 option has been deprecated but is still supported in this implementation.
+.Pp
+The
+.Fl u
+option is a non-standard extension.
 .Sh SEE ALSO
 .Xr execvp 3 ,
 .Xr environ 7
@@ -114,6 +134,16 @@
 .Nm
 utility conforms to
 .St -p1003.2-92 .
+.Sh HISTORY
+The
+.Nm
+command appeared in
+.Bx 4.4 .
+.Pp
+The
+.Fl u
+option first appeared in
+.Nx 10 .
 .Sh BUGS
 .Nm
 doesn't handle commands with equal
Index: env.c
===================================================================
RCS file: /cvsroot/src/usr.bin/env/env.c,v
retrieving revision 1.20
diff -u -r1.20 env.c
--- env.c	16 Nov 2010 02:53:49 -0000	1.20
+++ env.c	8 Feb 2020 10:21:01 -0000
@@ -60,13 +60,17 @@
 	setprogname(*argv);
 	(void)setlocale(LC_ALL, "");
 
-	while ((ch = getopt(argc, argv, "-i")) != -1)
+	while ((ch = getopt(argc, argv, "-iu:")) != -1)
 		switch((char)ch) {
 		case '-':			/* obsolete */
 		case 'i':
 			environ = cleanenv;
 			cleanenv[0] = NULL;
 			break;
+		case 'u':
+			if (unsetenv(optarg) == -1)
+				errx(EXIT_FAILURE, "unsetenv %s", optarg);
+			break;
 		case '?':
 		default:
 			usage();
@@ -93,7 +97,8 @@
 static void
 usage(void)
 {
-	(void)fprintf(stderr, "Usage: %s [-i] [name=value ...] [command]\n",
+	(void)fprintf(stderr,
+	    "Usage: %s [-i] [-u name] [name=value ...] [command]\n",
 	    getprogname());
 	exit(1);
 }