? a.out
Index: env.1
===================================================================
RCS file: /cvsroot/src/usr.bin/env/env.1,v
retrieving revision 1.13
diff -u -r1.13 env.1
--- env.1	8 Feb 2020 10:30:22 -0000	1.13
+++ env.1	8 Feb 2020 10:57:03 -0000
@@ -40,7 +40,7 @@
 .Nd set and print environment
 .Sh SYNOPSIS
 .Nm
-.Op Fl i
+.Op Fl 0i
 .Op Fl u Ar name
 .Op Ar name=value ...
 .Oo
@@ -86,10 +86,17 @@
 .Ar utility
 is specified,
 .Nm
-prints out the names and values
-of the variables in the environment, with one
+prints out the names and values of the variables in the environment.
+Each
 .Ar name=value
-pair per line.
+pair is separated by a new line unless
+.Fl 0
+is specified, in which case name/value pairs are separated by NUL.
+Both
+.Fl 0
+and
+.Ar utility
+must not be specified together.
 .Sh EXIT STATUS
 .Nm
 exits with one of the following values:
@@ -111,6 +118,11 @@
 see its manual page for more information.
 In this case the exit code is returned by the utility itself, not
 .Nm .
+.It 125
+.Ar utility
+was specified together with the
+.Fl 0
+option.
 .It 126
 .Ar utility
 was found, but could not be invoked.
@@ -125,7 +137,9 @@
 .Pp
 The
 .Fl u
-option is a non-standard extension.
+and
+.Fl 0
+options are non-standard extensions.
 .Sh SEE ALSO
 .Xr execvp 3 ,
 .Xr environ 7
@@ -142,7 +156,9 @@
 .Pp
 The
 .Fl u
-option first appeared in
+and
+.Fl 0
+optionss first appeared in
 .Nx 10 .
 .Sh BUGS
 .Nm
Index: env.c
===================================================================
RCS file: /cvsroot/src/usr.bin/env/env.c,v
retrieving revision 1.22
diff -u -r1.22 env.c
--- env.c	8 Feb 2020 10:36:02 -0000	1.22
+++ env.c	8 Feb 2020 10:57:03 -0000
@@ -54,15 +54,19 @@
 int
 main(int argc, char **argv)
 {
-	char **ep;
+	char **ep, term;
 	char *cleanenv[1];
 	int ch;
 
 	setprogname(*argv);
 	(void)setlocale(LC_ALL, "");
 
-	while ((ch = getopt(argc, argv, "-iu:")) != -1)
+	term = '\n';
+	while ((ch = getopt(argc, argv, "-0iu:")) != -1)
 		switch((char)ch) {
+		case '0':
+			term = '\0';
+			break;
 		case '-':			/* obsolete */
 		case 'i':
 			environ = cleanenv;
@@ -82,7 +86,11 @@
 
 	if (*argv) {
 		/* return 127 if the command to be run could not be found; 126
-		   if the command was found but could not be invoked */
+		   if the command was found but could not be invoked; 125 if
+		   -0 was specified with utility.*/
+
+		if (term == '\0')
+			errx(125, "cannot specify command with -0");
 
 		(void)execvp(*argv, argv);
 		err((errno == ENOENT) ? 127 : 126, "%s", *argv);
@@ -90,7 +98,7 @@
 	}
 
 	for (ep = environ; *ep; ep++)
-		(void)printf("%s\n", *ep);
+		(void)printf("%s%c", *ep, term);
 
 	exit(0);
 }
@@ -99,7 +107,7 @@
 usage(void)
 {
 	(void)fprintf(stderr,
-	    "Usage: %s [-i] [-u name] [name=value ...] [command]\n",
+	    "Usage: %s [-0i] [-u name] [name=value ...] [command]\n",
 	    getprogname());
 	exit(1);
 }