Check if an IP (IPv4) address is valid in Jsonnet, a simple example.

scrtipt.sh

$ cat test.jsonnet 
local validateIP(ip) =
  local aux(value) =
    local mask = std.parseHex("ffffffff");
    local octets = std.prune([if x != "" then std.parseInt(x) else null for x in std.split(value, '.')]);
    if std.length(octets) != 4 then
      false
    else
      local masked = ((octets[0] << 24) | (octets[1] << 16) | (octets[2] << 8) | (octets[3] << 0) & mask);
      if masked < 0 then false else masked <= mask;
  aux(ip);

{
  a: validateIP("0.0.0.0"),
  b: validateIP("255.255.255.255"),
  c: validateIP("192.168.1.0"),
  d: validateIP("192.168.1.1"),
  e: validateIP("255.255.255.0"),
  f: validateIP("359.63.9.234"), // IP address from the "CSI Miami" TV series.
  g: validateIP("1.2.3"),
  h: validateIP("1.2.3."),
  i: validateIP(".2.3.4"),
  j: validateIP(""),
  k: validateIP("-1.1.1.1"),
}

$ jsonnet test.jsonnet 
{
   "a": true,
   "b": true,
   "c": true,
   "d": true,
   "e": true,
   "f": false,
   "g": false,
   "h": false,
   "i": false,
   "j": false,
   "k": false
}