2 files changed, 18 insertions, 8 deletions

diff --git a/usr.bin/make/job.c b/usr.bin/make/job.c
index 49497b3b4e68..c2df52b6385a 100644
--- a/usr.bin/make/job.c
+++ b/usr.bin/make/job.c
@@ -316,6 +316,8 @@ struct Shell {
 
 	ArgArray builtins;
 	char	*meta;
+
+	Boolean	unsetenv;	/* unsetenv("ENV") before exec */
 };
 TAILQ_HEAD(Shells, Shell);
 
@@ -409,7 +411,7 @@ static const char *const shells_init[] = {
 	"quiet='set -' echo='set -v' filter='set -' "
 	"hasErrCtl=Y check='set -e' ignore='set +e' "
 	"echoFlag=v errFlag=e "
-	"meta='" SH_META "' builtins='" SH_BUILTINS "'",
+	"meta='" SH_META "' builtins='" SH_BUILTINS "' unsetenv=T",
 
 	NULL
 };
@@ -646,13 +648,6 @@ Proc_Init()
 	sa.sa_flags = SA_RESTART | SA_NOCLDSTOP;
 	sa.sa_handler = catch_child;
 	sigaction(SIGCHLD, &sa, NULL);
-
-#if DEFSHELL == 2
-	/*
-	 * Turn off ENV to make ksh happier.
-	 */
-	unsetenv("ENV");
-#endif
 }
 
 /**
@@ -698,6 +693,11 @@ ProcExec(const ProcStuff *ps)
 			Punt("Cannot dup2: %s", strerror(errno));
 	}
 
+	if (commandShell->unsetenv) {
+		/* for the benfit of ksh */
+		unsetenv("ENV");
+	}
+
 	/*
 	 * The file descriptors for stdin, stdout, or stderr might
 	 * have been marked close-on-exec.  Clear the flag on all
@@ -2582,6 +2582,7 @@ JobShellDump(const struct Shell *sh)
 	for (i = 1; i < sh->builtins.argc; i++)
 		fprintf(stderr, " '%s'", sh->builtins.argv[i]);
 	fprintf(stderr, "\n  meta='%s'\n", sh->meta);
+	fprintf(stderr, "  unsetenv=%d\n", sh->unsetenv);
 }
 
 /**
@@ -2670,6 +2671,10 @@ JobParseShellSpec(const char *spec, Boolean *fullSpec)
 			free(sh->meta);
 			sh->meta = estrdup(eq);
 			*fullSpec = TRUE;
+		} else if (strcmp(keyw, "unsetenv") == 0) {
+			sh->unsetenv = (*eq == 'Y' || *eq == 'y' ||
+			    *eq == 'T' || *eq == 't');
+			*fullSpec = TRUE;
 		} else {
 			Parse_Error(PARSE_FATAL, "unknown keyword in shell "
 			    "specification '%s'", keyw);
diff --git a/usr.bin/make/make.1 b/usr.bin/make/make.1
index 2afbe2e29582..a9e6e1ef9412 100644
--- a/usr.bin/make/make.1
+++ b/usr.bin/make/make.1
@@ -1325,6 +1325,11 @@ character not starts with a shell builtin it is executed directly without
 invoking a shell.
 When one of these strings (or both) is empty all commands are executed
 through a shell.
+.It Va unsetenv
+If true remove the
+.Ev ENV
+environment variable before executing any command.
+This is useful for the Korn-shell ksh.
 .El
 .Pp
 Values that are strings must be surrounded by double quotes.