#!/usr/bin/awk -f
{
    for (i = 1; i <= NF; i++) {
	ip = $i
	if (ip ~ /^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$/)
		if (host[ip])
			$i = host[ip]
		else {
			cmd = "/usr/bin/host 2>/dev/null " ip
			if ((cmd | getline line) > 0) {
				sub(/.* /, "", line)
				if (line) {
					$i = line
					host[ip] = line
				}
				else
					host[ip] = $i
			}
			else
				host[ip] = $i
			close (cmd)
		}
    }
    print
}

END {
    exit 0
}