shell: improved online documentation for txtsnd

examples/default/README.md

@@ -53,7 +53,7 @@ Running the `help` command on an iotlab-m3:
 2015-09-16 16:57:17,742 - INFO # lsm303dlhc_init      Initializes the lsm303dlhc sensor driver.
 2015-09-16 16:57:17,744 - INFO # lsm303dlhc_read      Prints data from the lsm303dlhc sensor.
 2015-09-16 16:57:17,746 - INFO # ifconfig             Configure network interfaces
-2015-09-16 16:57:17,747 - INFO # txtsnd               send raw data
+2015-09-16 16:57:17,747 - INFO # txtsnd               Sends a custom string as is over the link layer
 ```
 
 Running the `ps` command on an iotlab-m3:

examples/posix_sockets/README.md

@@ -44,7 +44,7 @@ Running the `help` command on an iotlab-m3:
 2015-09-22 14:54:54,451 - INFO # mersenne_init        initializes the PRNG
 2015-09-22 14:54:54,453 - INFO # mersenne_get         returns 32 bit of pseudo randomness
 2015-09-22 14:54:54,454 - INFO # ifconfig             Configure network interfaces
-2015-09-22 14:54:54,455 - INFO # txtsnd               send raw data
+2015-09-22 14:54:54,455 - INFO # txtsnd               Sends a custom string as is over the link layer
 2015-09-22 14:54:54,457 - INFO # ncache               manage neighbor cache by hand
 2015-09-22 14:54:54,459 - INFO # routers              IPv6 default router list
 ```

sys/shell/commands/sc_netif.c

@@ -840,7 +840,7 @@ int _netif_send(int argc, char **argv)
     uint8_t flags = 0x00;
 
     if (argc < 4) {
-        printf("usage: %s <if> [<addr>|bcast] <data>\n", argv[0]);
+        printf("usage: %s <if> [<L2 addr>|bcast] <data>\n", argv[0]);
         return 1;
     }
 

sys/shell/commands/shell_commands.c

@@ -176,7 +176,7 @@ const shell_command_t _shell_command_list[] = {
 #endif
 #ifdef MODULE_GNRC_NETIF
     {"ifconfig", "Configure network interfaces", _netif_config},
-    {"txtsnd", "send raw data", _netif_send },
+    {"txtsnd", "Sends a custom string as is over the link layer", _netif_send },
 #endif
 #ifdef MODULE_FIB
     {"fibroute", "Manipulate the FIB (info: 'fibroute [add|del]')", _fib_route_handler},