Reset users passwords using shell script

rahmad · 08-05-2008, 10:34 AM

hi all,

I need someone please to provide me with shell/bash script that reset users' passwords. this script should read the usernames list from a file and the passwords list from another file. the usernames and passwords files format is entry per line.

please help!!

thx
rahmad

colucix · 08-05-2008, 10:39 AM

How about your experience with shell scripting? What have you tried so far?

rahmad · 08-05-2008, 11:05 AM

I am not that good in writing scripts. I think I need two nested loops.
I tried that before a long time but it didnt work. now I need it urgently and quickly because that I posted it here now.

please send me the script if you know it?

thanks in advance

colucix · 08-05-2008, 11:26 AM

Using two nested loops is more difficult, since you have to read both files one line at a time. You can previously merge the two files side by side, then read the two fields in a single while loop. You can also do this on the fly. Suppose you have two files called users and passwd:

Code:

$ cat users
user1
user2
user3
$ cat passwd
passwd1
passwd2
passwd3

you can pass the output of the paste command, which merges the files side by side, to the while loop using process substitution. The syntax is:

Code:

#!/bin/bash
while read user passwd
do
  echo user is $user   password is $passwd
done < <(paste -d\  users passwd)

As you can see the read statement can read two (or more) variables simultaneously. Running this script gives

Code:

$ ./test.sh
user is user1 password is passwd1
user is user2 password is passwd2
user is user3 password is passwd3

Then you have only to write the proper command to reset users' passwords. Hope this helps.

kenoshi · 08-05-2008, 12:15 PM

Why does this sound like a homework assignment

Anyway, to add to colucix's excellent advice, use an expect script to actually change the password. If you don't have it, use the package management utility for your distro and install it.

Once that's done, create an expect script called changepw.exp as follows:

Code:

#!/usr/bin/expect -f
set username [lrange $argv 0 0]
set password [lrange $argv 1 1]
set timeout -1

spawn passwd $username
expect "*?assword:*"
send -- "$password\r"
expect "Retype*"
send -- "$password\r"
expect eof

And just change colucix's example as follows:

Code:

#!/bin/bash
while read user passwd
do
  changepw.exp $user $passwd
done < <(paste -d\  users passwd)

Should work just fine. Hope this helps.

colucix · 08-05-2008, 12:32 PM

Good call, kenoshi. However I think the --stdin option of passwd is enough. I would try something like

Code:

echo "$passwd" | passwd --stdin "$user"

It should work fine as well.

Just a side note: if the passwords contain some special characters, most likely they must be escaped. For example a literal backslash \ should be escaped with another backslash \\ so that the script can interpret it correctly.

kenoshi · 08-05-2008, 05:50 PM

Ah nice, didn't know about the --stdin option, thanks for the great tip!

rahmad · 08-05-2008, 05:51 PM

hi colucix,

after using the merged file, how can I extract from each line the username and password and put them on two different place holders in order to use them in echo "$passwd" | passwd --stdin "$user"

I guess we may need to use awk, is that right?? I would appreciate if you send me the complete script

thx

colucix · 08-06-2008, 01:24 AM

Quote:

Originally Posted by rahmad

I would appreciate if you send me the complete script

I have already done... and kenoshi too...

rahmad · 08-06-2008, 03:13 PM

thanks, its done now

but you made a mistake when you put -d\ in done < <(paste -d\ users passwd)

for all newbie this is the complete script:

while read user passwd
do
echo "$passwd" | passwd --stdin "$user"
done < <(paste user passwd)

cheers

kenoshi · 08-06-2008, 05:55 PM

No he didn't, its 2 spaces after -d\ not one, he's replacing tab with space as delimiter. Its the same as saying:

-d" "

His way is more elegant

estabroo · 08-06-2008, 11:50 PM

well if you aren't tied to an actual shell script perl has modules on cpan for modifying password entries and I'm pretty sure python has something similar.

Gux · 09-01-2008, 06:12 PM

Hi, Rahmad and the rest:
I am, in fact, totally newbie to linux. I'm trying to add a bunch of users using scripts but I got stuck setting users' password via script and I found this thread. Could you please be more specific on your code? Is that a .sh file? Did you use a separate files or a single one for the user/pass pairs?
Thanks beforehand,

Gux.

Quote:

Originally Posted by rahmad

thanks, its done now

but you made a mistake when you put -d\ in done < <(paste -d\ users passwd)

for all newbie this is the complete script:

while read user passwd
do
echo "$passwd" | passwd --stdin "$user"
done < <(paste user passwd)

cheers

rahmad · 09-02-2008, 04:04 AM

hi

you have to put the code below in .sh file and then make the file executable by running chmod u+x file.sh

you should have also two another files in the same file.sh's location one for users and the other for passwords.

I suggest you to do a little reading about bash scripting

good luck