The problem is not clear. At least to somebody like me who knows little
about IP addresses. I assumed:
the "keys" are in lines with four fields, in the second field, before the
first (and only?) "::";
the lines to rewrite have two fields, the key being before one of the ":" in
the second field (I consider prefixes of growing size).
Here is a solution with AWK:
#!/usr/bin/awk -f
BEGIN {
while (getline < ARGV[1])
if (NF == 4)
{
split($2, a, "::")
m[a[1]] = $2 " " $3 " " $4
}
}
NF == 2 {
n = split($2, a, ":")
k = a[1]
for (i = 1; !(k in m) && ++i
