Added adaptable network device name (#283)

* Added adaptable network device name

updated script to use a user-defined variable for network device name to make it easier for users to adapt the script to wireless or Debian-standard 'predictable network names.'

* Update 20-raspibolt-welcome

raspibolt/resources/20-raspibolt-welcome

@@ -15,9 +15,12 @@ color_gray='\033[0;37m'
 bitcoin_dir="/home/bitcoin/.bitcoin"
 lnd_dir="/home/bitcoin/.lnd"
 
-#set external HDD. Set to mount point of blockchain volume
+#Set to mount point of blockchain volume. This is used to calculate USB HDD usage %
 ext_hdd="/mnt/hdd" 
 
+#Set to network device name (usually eth0 for ethernet or wlan0 for wireless on raspberry pi unless you have 'Predictable Network Names' turned on in raspi-config. To get network device name run ifconfig.)
+network_name="eth0"
+
 # get uptime & load
 load=$(w | grep "load average:" | cut -c11-)
 
@@ -54,8 +57,8 @@ else
 fi
 
 # get network traffic
-network_rx=$(ifconfig eth0 | grep 'RX packets' | awk '{ print $6$7 }' | sed 's/[()]//g')
-network_tx=$(ifconfig eth0 | grep 'TX packets' | awk '{ print $6$7 }' | sed 's/[()]//g')
+network_rx=$(ifconfig ${network_name} | grep 'RX packets' | awk '{ print $6$7 }' | sed 's/[()]//g')
+network_tx=$(ifconfig ${network_name} | grep 'TX packets' | awk '{ print $6$7 }' | sed 's/[()]//g')
 
 # Bitcoin blockchain
 btc_path=$(command -v bitcoin-cli)