Greetings,
In regards to this question, I'm curious about something.
cat /etc/passwd |grep "/bin/bash" |grep "[5-9][0-9][0-9]" |cut -d: -f1
This would list all users who are added to the system...How to modify it to make it look like it's an entry of /etc/aliases ? I mean how to add the results in the format of this, "allusers: user1, user2, user3, user4" ? Can anyone help?

awk -F: '$3 > 500 {print $1}' /etc/passwd


Cheers,
Tink

Well mine does the listing properly and more accurately,

The outputs are as follows:

[root@dns root]# awk -F: '$3 > 500 {print $1}' /etc/passwd
nfsnobody
shark


[root@dns root]# cat /etc/passwd |grep "/bin/bash" |grep "[5-9][0-9][0-9]" |cut -d: -f1
rony
shark
[root@ronydns root]#


The last output shows the real users who were added using adduser. I just wanna furnish it to add it to /etc/aliases so that sending email to one alias sends mail to everyone.

On my system I get all users with IDs greater 500 with both
methods ... no idea how you have set-up your passwd file,
and why the shell should make a difference.

That aside: if you take your method to a distro where new users
start with 1000 you won't get any sensible output.

If the shell was important it could easily be added to the awk.

Lastly: my method is more elegant ;}


Cheers,
Tink

Another question I would like ask is that is it possible to add several users by reading from a text file ? As for example, there are 20 users listed in the file users.txt. If they're to be added in the system using the useradd command, is it possible to do so using useradd, like the example u stated lists all users having UID > 500 in one single line? Thanks in advance.

man newusers

Not quite in a single line, but in a file with single lines :}


Cheers,
Tink

Good advice tinkster..........

This will print the user with user id greater than 500

cat /etc/passwd | awk -F ":" '{if($3>500){ print $1}}'

I realize there have been no post in over 6 months, but none of the previous replies provide what I'm looking for.

Is there a single command or one liner that I could use on a Red Hat system to list all userids that can potentially access the system?

On AIX I can issue the command lsuser -R files ALL to list every userid and the attributes contained in the local security registry (i.e., the various /etc/* security files). For example:
====================================================================================================
> lsuser -R files ALL
root id=0 pgrp=system groups=system,bin,sys,security,cron,audit,lp home=/ shell=/usr/bin/ksh auditclasses=general login=true su=true rlogin=true daemon=true admin=true sugroups=ALL admgroups= tpath=nosak ttys=ALL expires=0 auth1=SYSTEM auth2=NONE umask=22 registry=files SYSTEM=compat logintimes= loginretries=0 pwdwarntime=10 account_locked=false minage=0 maxage=0 maxexpired=-1 minalpha=0 minother=0 mindiff=0 maxrepeats=0 minlen=0 histexpire=0 histsize=0 pwdchecks= dictionlist= default_roles= fsize=-1 cpu=-1 data=-1 stack=-1 core=-1 rss=-1 nofiles=2000 time_last_login=1523384199 time_last_unsuccessful_login=1517419013 tty_last_login=/dev/pts/0 tty_last_unsuccessful_login=ssh host_last_login=prodigal1.unch.unc.edu host_last_unsuccessful_login=uncpmp.hprhs.com unsuccessful_login_count=0 roles=
daemon id=1 pgrp=staff groups=staff home=/etc login=true su=true rlogin=true daemon=true admin=true sugroups=ALL admgroups= tpath=nosak ttys=ALL expires=0101000070 auth1=SYSTEM auth2=NONE umask=22 registry=files SYSTEM=compat logintimes= loginretries=0 pwdwarntime=10 account_locked=false minage=0 maxage=13 maxexpired=-1 minalpha=2 minother=2 mindiff=0 maxrepeats=2 minlen=8 histexpire=26 histsize=0 pwdchecks= dictionlist= default_roles= fsize=2097151 cpu=-1 data=262144 stack=65536 core=2097151 rss=65536 nofiles=2000 roles=
bin id=2 pgrp=bin groups=bin,sys,adm home=/bin login=true su=true rlogin=true daemon=true admin=true sugroups=ALL admgroups= tpath=nosak ttys=ALL expires=0101000070 auth1=SYSTEM auth2=NONE umask=22 registry=files SYSTEM=compat logintimes= loginretries=0 pwdwarntime=10 account_locked=false minage=0 maxage=13 maxexpired=-1 minalpha=2 minother=2 mindiff=0 maxrepeats=2 minlen=8 histexpire=26 histsize=0 pwdchecks= dictionlist= default_roles= fsize=2097151 cpu=-1 data=262144 stack=65536 core=2097151 rss=65536 nofiles=2000 roles=
<snip>
====================================================================================================

lsuser -R LDAP ALL would list all userids from the LDAP security registry.
lsuser ALL would list all userids from both the local ("files") and LDAP security registries (plus any other security registries defined to the system).

Thanks.

Over 6 months? Over 6 years would be closer.
To list all users known by the system try

Thanks.
I'll look into the getent command. Hopefully it has an option to retrieve security information from multiple security files like the AIX lsuser command.

Never used and never heard Getent, this wiki link below shows how useful the command is.

https://en.wikipedia.org/wiki/Getent

Example from link above:

You must use more commands to get additional information. For example:
(Works fine with the Linux/BSD groups command. The SysV groups command is a little different.)

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