What's the most elegant way to add Redis to /etc/services?

A single line sort that puts it in the right place:

echo -e "redis\t\t6379/tcp" | sort -k2 -n -o /etc/services -m - /etc/services

Nothing in the rules against answering my own question - this one uses Redis exclusively:

cat /etc/services | redis-cli -x SET services; redis-cli --raw EVAL 'local s = redis.call("GET", KEYS[1]) local b, p, name, port, proto; p = 1 repeat b, p, name, port, proto = string.find(s, "([%a%w\-]*)%s*(%d+)/(%w+)", p) if (p and tonumber(port) > tonumber(ARGV[2])) then s = string.sub(s, 1, b-1) .. ARGV[1] .. "\t\t" .. ARGV[2] .. "/" .. ARGV[3] .. "\t\t\t# " .. ARGV[4] .. "\n" .. string.sub(s, b, string.len(s)) return s end until not(p)' 1 services redis 6379 tcp "remote dictionary server" > /etc/services

Formatted Lua code:

local s = redis.call("GET", KEYS[1])
local b, p, name, port, proto

p = 1
repeat
    b, p, name, port, proto = string.find(s, "([%a%w\-]*)%s*(%d+)/(%w+)", p)
    if (p and tonumber(port) > tonumber(ARGV[2])) then
        s = string.sub(s, 1, b-1) .. ARGV[1] .. "\t\t" .. ARGV[2] 
        .. "/" .. ARGV[3] .. "\t\t\t# " .. ARGV[4] .. "\n" 
        .. string.sub(s, b, string.len(s))
        return s
    end 
until not(p)

Note: a similar challenge (https://gist.github.com/jorinvo/2e43ffa981a97bc17259#gistcomment-1440996) had inspired this answer. I chose a pure Lua script approach instead of leveraging Sorted Sets... although I could :)

How about a python script, Itamar?

It works on the notion of extracting the port number (called the index in the code) and if we are above 6378 but have not yet printed our Redis line, print it, then mark that sentinel true and just print all lines (including the one we are on) after.

#!/usr/bin/python
lines = open("/etc/services").readlines()
printed=False
for line in lines:
    if printed:
        print line.rstrip()
        continue
    datafields = line.split()
    if line[0] == "#":
        print line.rstrip()
    else:
        datafields = line.split()
        try:
            try:
                index,proto = datafields[1].split("/")
                index = int(index)
            except:
                index,proto = datafields[0].split("/")
                index = int(index)
            if index > 6378:
                if not printed:
                    print "redis           6379/tcp    #Redis DSS"
                    printed = True
            print line.rstrip()
        except:
            print datafields
            raise

The relevant section on my file for comparison:

gnutella-rtr    6347/tcp    # gnutella-rtr
#                          Serguei Osokine <[email protected]>
#               6348-6381  Unassigned
redis           6379/tcp    #Redis DSS
metatude-mds    6382/udp    # Metatude Dialogue Server
metatude-mds    6382/tcp    # Metatude Dialogue Server

Notice the line above Redis is a range. Short of breaking the range this is a workable solution for me. You could break the range but IMO this works just fine. Splitting the range seems a bit much for a simple, elegant script. Especially considering the likelihood most services files don't have the unassigned ranges listed (this is on OS X) - and that they are in a comment anyway.

UPDATE

If you don't care about the local file and it's comments, this gets you all currently assigned ports which are not Reserved or Discard-ed: curl -s http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv| awk -F',' '$4!~/(Discard|Unassigned|Reserved)/ && $1 && $2+0>0 && $1!~/FIX/ {printf "%-16s\t%s/%s\t#%s\n", $1,$2,$3,$4}' > /etc/services

The FIX test is because some of those lines have embedded newlines - which can be a pain in awk.