Find UUIDs in input (stdin or files) and replace them with new UUIDs

reuuid.awk

#!/usr/bin/awk -f
function uuid(_c, _r) {
    _c = "uuidgen"
    _c | getline _r
    close(_c)
    return _r
}

BEGIN {
    r = "[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{8}"
}

$0 ~ r {
    out = ""
    s = $0
    while (o = match(s, r)) {
        u = substr(s, RSTART, RLENGTH)
        if (o > 1) {
            out = out substr(s, 1, RSTART-1)
        }
        if (!(u in a)) {
            a[u] = uuid()
        }
        out = out a[u]
        s = substr(s, RLENGTH+1)
    }
    print out substr(s, RLENGTH+1)
}