[SOLVED] Dealing with duplicate usernames

as92 · 03-05-2013, 08:32 AM

Hi everyone. I have a script that creates user accounts from a list in a file, but I need to be able to deal with duplicate usernames.

I want to be able to add a number on the end of the username if there is a duplicate entry but I'm not sure how to do this.

This is my script so far:

Code:

#!/bin/bash

NEW_USERS="/home/users.txt"
HOME_BASE="/home/"

cat ${NEW_USERS} | \

while read USER
do

  if grep ${USER} "/etc/passwd"; then
    useradd -m -d ${HOME_BASE}${USER} ${USER}  << need to add a number here if it exists

  else
    useradd -m -d ${HOME_BASE}${USER} ${USER}
  
  fi

Any help would be much appreciated, thank you!

lykwydchykyn · 03-05-2013, 10:23 AM

Something like this might work:

Code:

#!/bin/bash

NEW_USERS="/home/users.txt"
HOME_BASE="/home/"

cat ${NEW_USERS} | \

while read USER
do

  if grep ${USER} "/etc/passwd"; then
    NUM=$(grep ${USER} "/etc/passwd" |wc -l)
    USER=$USER$NUM
  fi
    useradd -m -d ${HOME_BASE}${USER} ${USER}

The only problem with the approach of grepping /etc/passwd to determine duplicates is that you'll get false hits on a partial match. For example, if you have a user "sjohnson", grepping for "sjohns" will match. But at worst, you'll get false positives and needlessly have numbers on some user names.

suicidaleggroll · 03-05-2013, 10:33 AM

It would probably be more robust to use id instead of grepping /etc/passwd, then just cycle through numbers until id reports that nobody has that name yet.

Something like

Code:

#!/bin/bash

NEW_USERS="/home/users.txt"
HOME_BASE="/home/"

cat "$NEW_USERS" | \

while read USER; do
   id $USER > /dev/null 2>&1
   if [[ $? -eq 1 ]]; then
      useradd -m -d ${HOME_BASE}${USER} ${USER}
   else
      add=1
      id ${USER}${add} > /dev/null 2>&1
      while [[ $? -eq 0 ]]; do
         add=$((add+1))
         id ${USER}${add} > /dev/null 2>&1
      done
      useradd -m -d ${HOME_BASE}${USER}${add} ${USER}${add}
   fi
done

linosaurusroot · 03-05-2013, 10:50 AM

If you must grep then

Code:

grep ^${USER}: /etc/passwd

Other options include Perl with the getpwnam() function.

You'll want to lock the passwd file by linking it to pwtmp before you make changes and unlink it afterwards.

as92 · 03-05-2013, 11:02 AM

Thanks for the replies guys. I don't have to use grep at all, but I didn't know how to do it any other way.
I'll try the scripts you suggested and report back

Cheers again

as92 · 03-05-2013, 11:21 AM

I probably should have added that the file literally has a list of names, no passwords, id field etc.

I tried the solutions and it's not creating any accounts. Anyone got any advice of where to go from here?

Thanks!

linosaurusroot · 03-05-2013, 11:28 AM

Quote:

Originally Posted by as92

not creating any accounts

Are you running it as root?

as92 · 03-05-2013, 11:30 AM

I am indeed :/

shivaa · 03-05-2013, 11:53 AM

Why don't you try like:

Code:

echo -n "Enter new user to be created: "; read user
exuser=$(awk -v u=$user -F":" '$1 ~ /u/ {print $1}' /etc/passwd)
if [ $user == $exuser ]; then
useradd -m -d ${HOME_BASE}${USER} $USER$$num
fi

as92 · 03-06-2013, 07:23 AM

It needs to take the names from a file, rather than being entered manually. Anyone got any ideas?
Cheers

as92 · 03-06-2013, 07:42 AM

Works now, thanks all

shivaa · 03-06-2013, 07:52 AM

Quote:

Originally Posted by as92

It needs to take the names from a file, rather than being entered manually. Anyone got any ideas?
Cheers

Then take input from file... simple

Code:

while read -r user
do
exuser=$(awk -v u=$user -F":" '$1 ~ /u/ {print $1}' /etc/passwd)
if [ $user == $exuser ]; then
useradd -m -d ${HOME_BASE}${USER} $USER$num
fi
done < infile.txt