Get InetAddress list using regexp in Java

Question

Is there a way to use regular expressions and get a list of IP address? In my case, there are aliases defined with numbers in the system for each device interface and I need to fetch the list using aliases. For test systems, all aliases could map to the same device whereas in production it would differ.

For eg., I can have traffic1, traffic2, traffic3, etc., mapped to eth0, eth1.. so on in production. Where as all trafficX could be mapped to eth0 in tests.

Is there a way get the list of all IP address by passing traffic* or something like that?

@MauricePerry The aliases that are mentioned in the /etc/hosts for each device interface — Chandru, Feb 02 '18 at 08:59
Yes. I have to read the IP's via aliases and not via NetworkInterface names. Because RHEL 6 to 7 eth are renamed to ens. So, upon installation aliases will be set and code needs to read IP's via aliases. This way there will not be any code changes if RHEL version changes ! — Chandru, Feb 02 '18 at 10:28

score -1 · Accepted Answer · answered Feb 02 '18 at 10:49

This method reads the /etc/hosts and search a pattern:

private static InetAddress[] listIPs(String re) throws IOException {
    Pattern pat = Pattern.compile(re);
    try (InputStream stream = new FileInputStream("/etc/hosts");
            Reader reader = new InputStreamReader(stream, "UTF-8");
            BufferedReader in = new BufferedReader(reader)) {
        Set<InetAddress> result = new HashSet<>();
        String line = in.readLine();
        while (line != null) {
            String[] fields = line.split("\\s+");
            boolean found = false;
            for (int i = 1; !found && i < fields.length; ++i) {
                found = pat.matcher(fields[i]).matches();
            }
            if (found) {
                result.add(InetAddress.getByName(fields[0]));
            }
            line = in.readLine();
        }
        return result.toArray(new InetAddress[result.size()]);
    }
}

In your example, you could pass "traffic[0-9]+" for instance.

This works, Thanks! I was looking for some standard API in Java SDK that would perform this. Seems no. Anyway thanks again! — Chandru, Feb 05 '18 at 15:02

Get InetAddress list using regexp in Java

1 Answers1