Find and replace text in a passwd file....

[Jonathan Caplette_1]

Hi guys,

I wanna do a script to manage my users and I want to have a function that can deactivate user by replacing in the /etc/passwd file the crypted password with the * caracter...

Example:

User1:e94xsM0XKbu4E:367:230:User1 user:/home/User1:/bin/ksh

I want to replace "e94xsM0XKbu4E" by "*" to make the line in the file look like that:

User1:*:367:230:User1 user:/home/User1:/bin/ksh

I know that I can use sed to do that, but I don't clearly understand how it work?? Can somebody help me with that??

Thanks
Jonathan

[Chris Wilshaw · Accepted solution]

If you're on HP-UX 11.* you can simply use

passwd -l

to lock the account in this way.

[Stefan Farrelly]

cat /etc/passwd | grep User1 | sed 's/e94xsM0XKbu4E/*/' >/etc/passwd.new

mv /etc/passwd.new /etc/passwd
chmod 444 /etc/passwd


Sed simply looks for text (within the '/') and replaces it with the 2nd field (the '/*/').

[Ian Dennison_1]

In truth, what sed is generally used for is searching a file and replacing characters, creating a new file which is then written back over the original.

In this case,...

cat /etc/passwd |awk -vuser=$USER -F":" '$1 == user {$2="*"}{print $1":"$2":"$3":"$4":"$5":"$6":"$7}' >/etc/newpasswd
cp /tmp/newpasswd /etc/passwd

This script tested and approved for human consumption. Share and Enjoy! Ian

[James R. Ferguson]

Hi:

Editing the 'etc/passwd' directly isn't the safest mode in which to operate. You can easily accomplish what you want with:

# passwd -r files -l User1

This locks the account. In an untrusted system this puts a "*" in teh encrypted password field.

Regards!

...JRF...

[Jean-Louis Phelix]

hi,

cat /etc/passwd | sed 's;^\([^:]*\):[^:]*:\(.*\)$;\1:*:\2;'

will do it

- ^\([^:]*\): defines \1 as all chars from begining to first ':'
- [^:]*: defines password fields as all char up to next ':'
- \(.*\)$ defines \2 as all char up to end of line
- \1:*:\2 replace pattern by \1:*:\2

HTH

Jean-Louis.

[Jean-Louis Phelix]

Hi,

Reading other's posts I must agree that it's not really the safest way of doing it ... But it shows you what sed and awk can do anyway :-)

Regards.

[Jonathan Caplette_1]

Haha!! Chris you're right!! I should have thought about that!! LOL!! passwd -l will do it!!!

BTW thanks all, I'll be able to use sed now!!!

ciao!

[H.Merijn Brand (procura]

If you don't understand how it works, my advice would be: don't.

If you ruin your password file, you'll disable your system, and you do not want that to happen!

a5:/tmp 113 > diff passwd /etc/passwd
a5:/tmp 114 > perl -pi -e'BEGIN{($usr,@ARGV)=(@ARGV,"passwd")}s/^$usr:[^:]+:/$usr:*:/' broomer
a5:/tmp 115 > diff passwd /etc/passwd a5:/tmp 116 > perl -pi -e'BEGIN{($usr,@ARGV)=(@ARGV,"passwd")}s/^$usr:[^:]+:/$usr:*:/' gert
a5:/tmp 117 > diff passwd /etc/passwd 18c18
< gert:*:201:200:G. Hoff,,26,0220717600:/u/usr/gert:/pro/bin/tcsh
---
> gert:4k3K1WTnC3SAg:201:200:G. Hoff,,26,0220717600:/u/usr/gert:/pro/bin/tcsh
Exit 1
a5:/tmp 118 >

Enjoy, have FUN! H.Merijn [don't break your sys]

[Caesar_3]

Hello!

You wanna lock user so don't do it by replace
the encripted passwd to "*" use option of passwd -l

That's do the job well.

Caesar

[Michael Kelly_5]

Jonathan,
you can try the following with awk

nullify_pw() {
rm /tmp/passwd-new >/dev/null 2>&1
cat /etc/passwd | gawk -v USER=$1 '
BEGIN {
FS = ":"
OFS = ":"
}
{
if ($1 == USER) {$2 = "*"; print
} else {
print
}
}' >>/tmp/passwd-new
cp /tmp/passwd-new /etc/passwd
}

and call nullify_pw with the username.

HTH,
Michael