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I know I can use finger command to display all the current users logged into the system. However, how can I list the users who are currently logged into the system more than once?

Jiaqi Yuan
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  • StackOverflow is dedicated to helping solve programming code problems. Your Q **may be** more appropriate for [su] , but read their help section regarding on-topic questions . AND please read [Help On-topic](https://stackoverflow.com/Help/On-topic) and [Help How-to-ask](https://stackoverflow.com/Help/How-to-ask) before posting more Qs here. Good luck. – shellter Jul 26 '20 at 02:00

3 Answers3

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Use the w command and parse its output

MatzZze
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Try

last | cut -d ' ' -f1  | sort |  uniq -c | grep -Ev 'reboot|wtmp'

last <-- last searches back through the /var/log/wtmp file (or the file designated by the -f option) and displays a list of all users logged in (and out) since that file was created.

cut -d ' ' -f1 <-- cut user name
sort -- Sort data
uniq -c <-- Get count of user
grep -Ev 'reboot|wtmp' <-- remove non required records

Digvijay S
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A crude bash script:

#!/bin/bash

arr=($(users))
tmp=${arr[0]}
cnt=1

for ((i = 1; i < ${#arr[@]}; ++i)); do
    if [ "$tmp" == "${arr[$i]}" ]; then
        cnt=$((cnt+1))
    else 
        if [ "$cnt" -gt "1" ]; then
            echo "${arr[$i]} is logged in more than once."
        fi
        tmp=${arr[$i]}
        cnt=1
    fi
done

if [ "$cnt" -gt "1" ]; then
    echo "${arr[$i]} is logged in more than once."
fi

Loop over an array created out of the output of users command.

Check if tmp is equal to the element coming after it:

if yes: echo,

else: change tmp to next element

NOTE:

arr=($(users)) should be avoided generally, but for this particular problem is doesn't cause issues.

SEE:

Reading output of a command into an array in Bash

Jacek Kuszmar
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