Hello once again,
a few days ago, I wrote the following message.
>I have been tasked with sending notifications to users when their
>account passwords are about to expire. I have been trying to
>determine the best way of determining this based upon the "passwd
>-sa" command which lists the following attributes for all accounts
>on the machine (white-space delimited):
>account_name status date_changed minimum_change maximum_change grace_period
>sysadmin PS 11/13/99 1 60 7
>which means the sysadmin account is active, the password was changed
>on 11/13/99, passwords must remain for at least a day, it must be
>changed within 60 days, and there is a 7 day grace period.
>While trying to tackle the problem, I thought it might be best to do
>calculations based upon "seconds from the epoch" However, I can not
>find any bourne shell level utilities to do conversions from date to
>"seconds from the epoch" and back. I know there are C libraries
>that could be used, but I would rather not have to worry about
>compiling code, and I am hesitant to do perl, as not all of our
>machines are loaded with it.
>Does anyone have any good ideas?
I got feedback from a number of people, including:
Marcos Assis Silva, Jonathan Loh, Karl Vogel, Jim lewinson, Daniel
Lorenzini, Brad Young, Rick Caldwell, Keith Willenson, Mark Anderson,
Renny Koshy, and Vince Merrell.
I thank you all for your input in my dilemma.
Marcos Assis Silva was nice enough to provide me with binaries and
source code of two utilities: cftime and mktime. They convert times
back and forth between normal "date" output and "seconds from epoch".
I almost used this, but decided on another utility (more info later).
- Thanks Marcos!
I got some recommendations to use the GNU date utility (gdate?)
Rick Caldwell sent me some scripts that perform a similar function to
what I was trying to do, but for temporary license keys. It mainly
uses awk for parsing license files. He even sent me a patch for Y2K
fixes. Thanks Rick.
I also got some recommendations to do Time Zone modifications to do
my date math.
And the winner is (drumroll please :-):
Jonathan Loh made me aware of a date utility called mktime (not the
same one as Marcos') put out by John R. Macmillan. It can be had at
compiled this snippet of code, followed the included man page, and
was able to complete my script quickly. I have included my script
below for anyone who is interested. It calls mktime, and uses it to
return a list of accounts that are about to expire. Thanks Jonathan!
(and of course John Macmillan)
# Copyright (c) 2000, by TKC Solutions, LLC
# Distributed as Freeware
# This script uses an executable compiled from the mktime source code from
# John R MacMillan (firstname.lastname@example.org) The source of mktime can be had at
# This script uses the "passwd -sa" command to get the list of accounts on the
# system, do some simple checking for accounts with expiration, and list those
# accounts that are due for changing soon. All commands are based upon syntax
# used in Sun Solaris 2.x as of January 2000.
#Modify as necessary for the path to the mktime, passwd, and grep binaries
export PSWD MKTIME GREP
# The following command parses the password file and singles out the accounts
# with exipiration.
$PSWD | $GREP PS | $GREP -v "00/00/00" > /tmp/passexp.dat
# This script assumes output of the passwd -sa command to have the following
# account_name status pw_chg_date [min_change] max_change warn_days
# min_change is optional, but all other arguments must be there.
while read nm st dt v1 v2 v3
# Today's date in seconds from the epoch
todaytime=`$MKTIME -F '%t' -z`
# Checking for minimum arguments
if [ "abc$v1" = "abc" -o "abc$v2" = "abc" ]
# if v3 is empty, then there was no min_change argument. Shift variables
# as if there were.
if [ "abc$v3" = "abc" ]
# get month date and year, convert 2 digit date to 4 digit date. I am using
# a 100 year window from 1991 through 2090.
# This Script is NOT Y2.091K compliant :-)
mo=`echo $dt | cut -b 1-2`
da=`echo $dt | cut -b 4-5`
yr=`echo $dt | cut -b 7-8`
if [ $yr -le 90 ]
yr=`expr $yr + 2000`
yr=`expr $yr + 1900`
# use mktime to calculate seconds since the epoch
chgtime=`$MKTIME -F '%t' -z -D "$yr-$mo-$da"`
# calculate password expiration date
duetime=`expr $chgtime + $v2 \* 86400 `
# convert expiration date back to normal date form
duedate=`$MKTIME -t $duetime`
# calculate how far we are from expiration and compare to warning value
difftime=`expr $duetime \- $todaytime`
diffday=`expr $difftime \/ 86400`
if [ $diffday -le $v3 ]
echo "account $nm has $diffday days left to change password.
grace period is
echo "account $nm expires on $duedate"
done < /tmp/passexp.dat
Jay Morgan Work E-Mail: email@example.com
Managing Partner Personal E-Mail: firstname.lastname@example.org
TKC Solutions LLC Phone: 770-671-8084 (use Mobile)
3380 Villa Robleda Dr. FAX: 650.618.1460
Mountain View, CA 94040
5125 Foxwood Ct. Home: 770-522-8611
Atlanta, GA 30360 Mobile: 770-329-4477
The surest way to corrupt a youth is to instruct him to hold in
higher regard those who think alike than those who think differently.
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