configure network interfaces with awk

Here a small script which allows to write /etc/network/interfaces cgi style.

I`ve written it since I search for a small project to learn a little bit more awk.

tested with debian squeeze, report me if it works also with other distributions.

 
#!/usr/bin/awk -f
# example call to set config value:
# ./interfaces interface=eth0 address=172.30.30.2
# options:
#   * address
#   * netmask
#   * gateway
#   * dns #
# interface param is required all others are optional
# also multible params can given
#
# example call to get current address value:
# ./interfaces get=address interface=eth0 interfaces
#
# example call to set hostname:
# ./interfaces hostname=newname
BEGIN {
 # we use all time the same input file so I define here which file to use
 ARGV[ARGC] = "/etc/network/interfaces"
 ARGC = ARGC + 1
}
{
if(hostname != "") {
 system("hostname " hostname)
 print hostname > "/etc/hostname"
 exit 0
}
 
if(get == "dns") {
 get_dns()
 exit 0
}
# interface is required its used as selector which we want modify
if(interface == "") {
 exit 1
}
 
# get value from interface configuration
 
if($1 == "iface" && $2 ~ interface && get != "") {
 get_if_val(get)
}
line[NR] = $0
# set value(s) to interface configuration
# all params are optional
if($1 == "iface" && $2 ~ interface && get == "") {
 cnf_if(address, netmask, gateway, dns)     }
}
 
# get one value from network interfaces
function get_if_val(get) {
 
 while($1 != "auto" && getline != 0) {
 if($1 == get) {
 print $2             exit 0
 }
 }
}
 
# configure interface
function cnf_if(address, netmask, gateway, dns) {
 
 while ($1 != "auto" && getline != 0) {
 
 if($1 == "address" && address != "") {
 sub(".*", address, $2)
 }
 
 if($1 == "netmask" && netmask != "") {
 sub(".*", netmask, $2)
 }
 
 if($1 == "gateway" && gateway != "") {
 sub(".*", gateway, $2)
 }
 
 if($1 == "dns-nameservers" && dns != "") {
 sub(".*", $1 " " dns, $0)
 }
 line[NR] = $0
}
 
# write configuration
for(i=1;i<=NR;i++) {
 print line[i] > "/etc/network/interfaces"
}
 
# restart interface
system("ifdown " interface)
system("ifup " interface) }
function get_dns() {
 while(getline != 0) {
 if($1 == "dns-nameservers") {
 sub("dns-nameservers ", "", $0)
 print $0
 exit 0
 }
 }
}