Nawk

# ns_passwd.awk --- access password file information
#
# Arnold Robbins, arnold@skeeve.com, Public Domain
# May 1993
# Revised October 2000
# Revised December 2010
#
# Reworked for namespaces June 2017, with help from
# Andrew J.: Schorr, aschorr@telemetry-investments.com

@namespace "passwd"

BEGIN {
    # tailor this to suit your system
    Awklib = "/usr/local/libexec/awk/"
}

function Init(    oldfs, oldrs, olddol0, pwcat, using_fw, using_fpat)
{
    if (Inited)
        return

    oldfs = FS
    oldrs = RS
    olddol0 = $0
    using_fw = (PROCINFO["FS"] == "FIELDWIDTHS")
    using_fpat = (PROCINFO["FS"] == "FPAT")
    FS = ":"
    RS = "\n"

    pwcat = Awklib "pwcat"
    while ((pwcat | getline) > 0) {
        Byname[$1] = $0
        Byuid[$3] = $0
        Bycount[++Total] = $0
    }
    close(pwcat)
    Count = 0
    Inited = 1
    FS = oldfs
    if (using_fw)
        FIELDWIDTHS = FIELDWIDTHS
    else if (using_fpat)
        FPAT = FPAT
    RS = oldrs
    $0 = olddol0
}

function awk::getpwnam(name)
{
    Init()
    return Byname[name]
}

function awk::getpwuid(uid)
{
    Init()
    return Byuid[uid]
}

function awk::getpwent()
{
    Init()
    if (Count < Total)
        return Bycount[++Count]
    return ""
}

function awk::endpwent()
{
    Count = 0
}