In this tutorial, we learn how to write a shell script to find IP address from multiple Linux servers. This is very helpful when doing some auditing on the servers.
Shell script can be used to find ethernet interface details and IP address/netmask assigned from multiple servers.
The script will also display interface name even if no IP address is set. Make sure you have authorized keys set so each server can be login using ssh without a password.
Shell Script to get IP address
In the following script, 'server_list.txt' file keeps the server lists and 'result.txt' file contains all output with servername and ip details.
#!/bin/bash
#we save to variable name of file with list of server
serverlist='server_list.txt'
#we save to variable list of servers from file
servers=`cat $serverlist`
#we save in variable name of file with results
result='result.txt'
#we get each server from servers variable
for server in $servers
do
#Printing servername to result file
echo -e "$server"> $result
#getting list of ethernet links via ifconfig command, and from all output we need onlu lines that have word link and starting with [a-z][a-z]*[0-9], and after we get first word from output
ips=`ssh root@${server{ "ifconfig -a | grep -o -e '[a-z][a-z]*[0-9]*[ ]*Link' |grep -v lo| perl -pe 's|^([a-z]*[0-9]*)[ ]*Link|\1|'"`
After for every ethernet link from ips variable
for ip in $ips
do
#we get ips, via ifconfig command, and grepping for inet addr script.
INET=`ssh root${server} "ifconfig $ip |grep -o -e 'inet addr:[^ ]*' | grep -o -e '[^:]*$'"`
#same for mask
MASK=`ssh $server "ifconfig $ip |grep -o -e 'Mask:[^ ]*' | grep -o -e '[^:]*$'"`
#this check if any ip assigned
if [ -x $INET ];
then
#if no ip we will get no ip address set
INET="no ip address set"
fi
#we check if we get mask
if [ -x $MASK ];
then
MASK="no mask address set"
fi
#and we put result to result file.
echo "$ip : $INET : $MASK" >> $result
done
#this print empty line to result file
echo “” >> $result
done
Sample Output
Server1#./ifconfig.sh.sh Server1#cat result.txt red eth0 : 91.197.140.34 : 255.255.255.0 eth1 : 192.168.33.34 : 255.255.255.0 venet0 : no ip address set
