Linux script to extract usernames from text file

Question

I am a beginner at scripting, but I created a text file called text.dat which contains only usernames in the file location /home/daniel/text.dat and I’m trying to run a script(called addusers.sh) which displays the names from that text file and will create a new user account on the system for each new user account specified in the text.dat file.

For each user account that is created, append a line entry to the /home/daniel/logs/useraccounts.log file. The line entry will contain the following information:

added | < user account name > | < day and time of creation >

. This is what I have so far:

 #!/bin/bash 
echo “cat text.dat” 
newuser= grep /home/daniel/text.dat 
sudo adduser $newuser

Answer 1

How can I add users to a Linux system, as listed in a file?

Something along the lines of the following should do if you want the process to be fully automated (run via eg sudo ./addusers.sh):

#!/bin/bash
# addusers.sh - Add users to system and output a log of same
# run as root or via sudo

usersfile=/home/daniel/text.dat
logfile=/home/daniel/logs/useraccounts.log

while read user; do
   echo "Adding $user"
   adduser --gecos "" --disabled-password $user
   echo "added | $user | `date` |" >> $logfile
done < $usersfile

With options (from the adduser manpage):

--disabled-password

Like --disabled-login, but logins are still possible (for example using SSH RSA keys) but not using password authentication.

(--disabled-login would work too I guess)

--gecos GECOS

Set the gecos field for the new entry generated. adduser will not ask for finger information if this option is given.

You can leave these options to adduser off if you want to specify a password and/or user info.

You can also specify how you want the day and time of creation specified via options to date, eg

$ date "+%Y-%m-%d %H%M"
2017-02-19 0330

Answer 2

The event you want to log is already being logged by Linux. Take a look at /var/log/auth.log and try to filter or parse it according to your particular need instead of trying to create your own log file.

Here's a sampling of the log in question:

Feb 19 10:23:47 localhost sudo:    larssend : TTY=pts/1 ; PWD=/home/larssend ; USER=root ; COMMAND=/usr/sbin/useradd -m -s /bin/bash -U tst
Feb 19 10:23:47 localhost sudo: pam_unix(sudo:session): session opened for user root by (uid=0)
Feb 19 10:23:47 localhost useradd[1661]: new group: name=tst, GID=1001
Feb 19 10:23:47 localhost useradd[1661]: new user: name=tst, UID=1001, GID=1001, home=/home/tst, shell=/bin/bash
Feb 19 10:23:48 localhost sudo: pam_unix(sudo:session): session closed for user root
Feb 19 10:23:50 localhost sudo:    larssend : TTY=pts/1 ; PWD=/home/larssend ; USER=root ; COMMAND=/usr/sbin/userdel -r tst
Feb 19 10:23:50 localhost sudo: pam_unix(sudo:session): session opened for user root by (uid=0)
Feb 19 10:23:50 localhost userdel[1667]: delete user 'tst'
Feb 19 10:23:50 localhost userdel[1667]: removed group 'tst' owned by 'tst'
Feb 19 10:23:50 localhost userdel[1667]: removed shadow group 'tst' owned by 'tst'
Feb 19 10:23:50 localhost sudo: pam_unix(sudo:session): session closed for user root

As you can see, it has pretty much everything you might need to know about user account creation and deletion, including who performed the creation/deletion by way of sudo logging. Note that if the creator didn't use sudo to call useradd or userdel, you may have to perform some extra work to figure out who performed the creation/deletion.