Upgrade netcat a lot. Make -e able to take the rest of the command line as

what to exec.  Add -f mode and a brief explanation of how to use it to replace
minicom.  Add -l -l mode so you can turn any command into a server.  And group
all of netcat's command line options under two CONFIG entries, so if you
disable both it doesn't use getopt at all.

2 files changed, 31 insertions, 12 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 6d6213901..af45511d4 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -19,6 +19,7 @@
 #include <fcntl.h>
 #include <inttypes.h>
 #include <netdb.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
diff --git a/include/usage.h b/include/usage.h
index 3c1fb18e9..7c63e2f85 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -2105,23 +2105,41 @@ USE_FEATURE_MDEV_CONFIG( \
         " or\n" \
         "$ nameif -c /etc/my_mactab_file\n" \
 
-#ifdef CONFIG_NC_GAPING_SECURITY_HOLE
-#  define USAGE_NC_EXEC(a) a
+#if ENABLE_NC_SERVER || ENABLE_NC_EXTRA
+#define NC_BR1 "["
+#define NC_BR2 "]"
 #else
-#  define USAGE_NC_EXEC(a)
+#define NC_BR1
+#define NC_BR2
 #endif
+
 #define nc_trivial_usage \
-        "[OPTIONS] [IP] [port]"
+        "[" \
+        NC_BR1 USE_NC_SERVER("-lp")USE_NC_EXTRA("iwf") NC_BR2 \
+        " ["USE_NC_EXTRA("FILENAME|")"{IPADDR PORTNUM}]"USE_NC_EXTRA(" [-e COMMAND]")
 #define nc_full_usage \
-        "Netcat opens a pipe to IP:port\n\n" \
-        "Options:\n" \
-        "\t-l\t\tlisten mode, for inbound connects\n" \
-        "\t-p PORT\t\tlocal port number\n" \
-        "\t-i SECS\t\tdelay interval for lines sent\n" \
-        USAGE_NC_EXEC( \
-        "\t-e PROG\t\tprogram to exec after connect (dangerous!)\n" \
+        "Netcat opens a pipe, either to IP:port\n\n" \
+        "Options:" \
+        USE_NC_EXTRA( \
+                "\n\t-e\t\texec rest of command line after connect\n" \
+                "\t-i SECS\t\tdelay interval for lines sent\n" \
+                "\t-w SECS\t\ttimeout for connect\n" \
+                "\t-f filename\tuse file (ala /dev/ttyS0) instead of network" \
         ) \
-        "\t-w SECS\t\ttimeout for connects and final net reads"
+        USE_NC_SERVER( \
+                "\n\t-l\t\tlisten mode, for inbound connects\n" \
+                USE_NC_EXTRA("\t\t\t(use -l twice with -e for persistent server)\n") \
+                "\t-p PORT\t\tlocal port number" \
+        )
+
+
+#define nc_notes_usage "" \
+        USE_NC_EXTRA( \
+                "To use netcat as a terminal emulator on a serial port:\n\n" \
+                "$ stty 115200 -F /dev/ttyS0\n" \
+                "$ stty raw -echo -ctlecho && nc -f /dev/ttyS0\n" \
+        ) ""
+
 #define nc_example_usage \
         "$ nc foobar.somedomain.com 25\n" \
         "220 foobar ESMTP Exim 3.12 #1 Sat, 15 Apr 2000 00:03:02 -0600\n" \