Encontrei alguns erros no seu script. Aqui está como eu acho que deveria ser (supondo que estas são as coisas que você quer fazer este script):
#!/bin/bash
getinfo()
{
read -p "Enter the IP of your router: (looks like 192.168.1.1) " routerip
read -p "Enter the netmask for your network: (looks like 255.255.255.0) " netmask
read -p "Enter the ip address for your server: (looks like 192.168.1.22) " staticip
}
writeinterfacefile()
{
cat << EOF >
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto eth0
iface eth0 inet dhcp
#Your static network configuration
iface eth0 inet static
address $staticip
netmask $netmask
gateway $routerip
EOF
#don't use any space before of after 'EOF' in the previous line
echo ""
echo "Your informatons was saved in '' file."
echo ""
exit 0
}
file="/home/radu/test"
if [ ! -f $file ]; then
echo ""
echo "The file '$file' doesn't exist!"
echo ""
exit 1
fi
clear
echo "Let's set up a static ip address for your site"
echo ""
getinfo
echo ""
echo "So your settings are:"
echo "Address of your Router is: $routerip"
echo "The Mask for the Network is: $netmask"
echo "Your decided Server IP is: $staticip"
echo ""
while true; do
read -p "Are these informations correct? [y/n]: " yn
case $yn in
[Yy]* ) writeinterfacefile $file;;
[Nn]* ) getinfo;;
* ) echo "Pleas enter y or n!";;
esac
done