? o
Index: builtins.def
===================================================================
RCS file: /cvsroot/src/bin/sh/builtins.def,v
retrieving revision 1.23
diff -u -u -r1.23 builtins.def
--- builtins.def	10 May 2015 20:30:54 -0000	1.23
+++ builtins.def	31 Oct 2016 20:52:16 -0000
@@ -49,6 +49,7 @@
 bgcmd -j	-u bg
 breakcmd	-s break -s continue
 cdcmd		-u cd chdir
+cloexeccmd	cloexec
 dotcmd		-s .
 echocmd		echo
 evalcmd		-s eval
Index: redir.c
===================================================================
RCS file: /cvsroot/src/bin/sh/redir.c,v
retrieving revision 1.47
diff -u -u -r1.47 redir.c
--- redir.c	12 May 2016 13:31:37 -0000	1.47
+++ redir.c	31 Oct 2016 20:52:16 -0000
@@ -55,6 +55,7 @@
  */
 
 #include "main.h"
+#include "builtins.h"
 #include "shell.h"
 #include "nodes.h"
 #include "jobs.h"
@@ -551,3 +552,52 @@
 	(void)fcntl(fd, F_SETFD, FD_CLOEXEC);
 	return fd;
 }
+
+static void
+printone(int fd, int p)
+{
+	int c;
+	if ((c = fcntl(fd, F_GETFD)) == -1) {
+		if (!p)
+			return;
+		error("Can't get status for fd=%d (%s)", fd, strerror(errno));
+	}
+	outfmt(out1, "%c%d\n", "-+"[c & FD_CLOEXEC], fd);
+}
+
+static void
+setone(int fd, int how)
+{
+	if ((fcntl(fd, F_SETFD, how)) == -1)
+		error("Can't %s close-on-exec for fd=%d (%s)", 
+		    how ? "set" : "clear", fd, strerror(errno));
+}
+
+int
+cloexeccmd(int argc, char *argv[])
+{
+	char *num;
+	argptr = argv + 1;
+
+	if (!*argptr) {
+		int maxfd = fcntl(0, F_MAXFD);
+		if (maxfd == -1)
+			error("Can't get max fd (%s)", strerror(errno));
+		for (int i = 0; i <= maxfd; i++)
+			printone(i, 0);
+		return 0;
+	}
+	while ((num = *argptr++) != NULL) {
+		char c;
+		switch (c = *num) {
+		case '+': case '-':
+			num++;
+			break;
+		default:
+			printone(atoi(num), 1);
+			continue;
+		}
+		setone(atoi(num), c == '+' ? FD_CLOEXEC : 0);
+	}
+	return 0;
+}