--- src/usr.bin/nc/netcat.c.7-execcmd	2005-10-12 19:24:33 +0400
+++ src/usr.bin/nc/netcat.c	2005-11-07 22:44:03 +0300
@@ -90,11 +90,13 @@ int	Dflag;					/* sodebug */
 int	Sflag;					/* TCP MD5 signature option */
 #endif
 int	Tflag = -1;				/* IP Type of Service */
+char	*opt_exec = NULL;			/* program to exec after connecting */
 
 int timeout = -1;
 int family = AF_INET;
 char *portlist[PORT_MAX+1];
 
+void	execcmd(int fd);
 void	atelnet(int, unsigned char *, unsigned int);
 void	build_ports(char *);
 void	help(void);
@@ -139,7 +141,7 @@
 		usage(1);
 
 	while ((ch = getopt(argc, argv,
-	    "46Ddhi:jklnP:p:rSs:tT:Uuvw:X:x:z")) != -1) {
+	    "46Dde:hi:jklnP:p:rSs:tT:Uuvw:X:x:z")) != -1) {
 		switch (ch) {
 		case '4':
 			family = AF_INET;
@@ -158,6 +160,11 @@ main(int argc, char *argv[])
 		case 'd':
 			dflag = 1;
 			break;
+		case 'e':   /* prog to exec */
+			if (opt_exec)
+				errx(1, "cannot specify `-e' option double");
+			opt_exec = strdup(optarg);
+			break;
 		case 'h':
 			help();
 			break;
@@ -257,6 +264,8 @@ main(int argc, char *argv[])
 		errx(1, "cannot use -p and -l");
 	if (lflag && zflag)
 		errx(1, "cannot use -z and -l");
+	if (zflag && opt_exec)
+		errx(1, "cannot use -z and -e");
 	if (!lflag && kflag)
 		errx(1, "must use -l with -k");
 
@@ -426,6 +435,45 @@ main(int argc, char *argv[])
 	exit(ret);
 }
 
+
+/*
+ *  execcmd()
+ *  Execute an external file making its stdin/stdout/stderr
+ *  the actual socket. Returns never.
+ */
+void
+execcmd(int fd)
+{
+	int saved_stderr;
+	char *p;
+
+	/* save the stderr fd because we may need it later */
+	saved_stderr = dup(STDERR_FILENO);
+
+	/* duplicate the socket for the child program */
+	dup2(fd, STDIN_FILENO);               /* the precise order of fiddlage */
+	close(fd);                            /* is apparently crucial; this is */
+	dup2(STDIN_FILENO, STDOUT_FILENO);    /* swiped directly out of "inetd". */
+	dup2(STDIN_FILENO, STDERR_FILENO);    /* also duplicate the stderr channel */
+
+	/* change the label for the executed program */
+	if ((p = strrchr(opt_exec, '/'))) {
+		p++;                          /* shorter argv[0] */
+	} else {
+		p = opt_exec;
+	}
+
+	/* replace this process with the new one */
+#ifndef USE_OLD_COMPAT
+	execl("/bin/sh", p, "-c", opt_exec, NULL);
+#else
+	execl(opt_exec, p, NULL);
+#endif
+	dup2(saved_stderr, STDERR_FILENO);
+	err(1, "couldn't execute %s ", opt_exec);
+}
+
+
 /*
  * unix_connect()
  * Returns a socket connected to a local unix socket. Returns -1 on failure.
@@ -629,6 +677,12 @@ readwrite(int nfd)
 	int lfd = fileno(stdout);
 	int plen;
 
+	if (opt_exec) {
+		if (vflag)
+			printf("Call sub-process %s\n", opt_exec);
+		execcmd(nfd);
+	}
+
 #if defined(HAVE_SO_JUMBO)
 	plen = jflag ? 8192 : 1024;
 #else
@@ -856,7 +910,7 @@ help(void)
 void
 usage(int ret)
 {
-	fprintf(stderr, "usage: netcat [-46DdhklnrStUuvz] [-i interval] [-p source_port]\n");
+	fprintf(stderr, "usage: netcat [-46DdhklnrStUuvz] [-e cmd] [-i interval] [-p source_port]\n");
 	fprintf(stderr, "              [-s source_ip_address] [-w timeout] [-X proxy_version]\n");
 	fprintf(stderr, "              [-x proxy_address[:port]] [hostname] [port[s]]\n");
 	if (ret)
--- src/usr.bin/nc/nc.1.7-execcmd	2006-07-25 15:33:54 +0400
+++ src/usr.bin/nc/nc.1	2006-07-25 15:34:49 +0400
@@ -35,6 +35,7 @@
 .Nm nc
 .Bk -words
 .Op Fl 46DdhklnrStUuvz
+.Op Fl e Ar command
 .Op Fl i Ar interval
 .Op Fl P Ar proxy_username
 .Op Fl p Ar source_port
@@ -97,6 +98,9 @@
 Enable debugging on the socket.
 .It Fl d
 Do not attempt to read from stdin.
+.It Fl e Ar command
+Starts specified command for communicating with remote side
+after connection is established.
 .It Fl h
 Prints out
 .Nm
@@ -399,6 +403,11 @@
 if the proxy requires it:
 .Pp
 .Dl $ nc -x10.2.3.4:8080 -Xconnect -Pruser host.example.com 42
+.Pp
+Listen on port 1234, send system name to connected client and exit:
+.Pp
+.Dl $ nc -l -v -e 'cat /etc/altlinux-release; uname -a' 1234
+.Pp
 .Sh SEE ALSO
 .Xr cat 1 ,
 .Xr ssh 1