remove duplicated lines without sort

Shell Programming and Scripting
1

Hi
Just wondering whether or not I can remove duplicated lines without sort

For example, I use the command who, which shows users who are logging on. In some cases, it shows duplicated lines of users who are logging on more than one terminal.

Normally, I would do

who | cut -d" " -f1 | sort |uniq

But I realised that I do not want data to be sorted.

Is there any other ways to do it?

2

Are the duplicated lines adjacent? If not which one do you remove?

3

Try follow one, use awk array to remember the appearance of the line:

awk '{
 if (arr[$0]=="")
 arr[$0]=1
 }
 END{
 for (i in arr)
 print i
 }' filename
4

I am new to awk or you can say UNIX. Honestly, I do not understand awk at the moment.
I will try to study it. :slight_smile:
Thank you for your reply anyway.

Duplicated lines are not adjacent and I can remove any of them.

Cheers,

5 
$ who
oracle     pts/1        Aug 21 04:57    (...)
oracle     pts/4        Aug 21 04:57    (...)
$ who|awk '!x[$1]++'
oracle     pts/1        Aug 21 04:57    (...)

If you want only the first field to be displayed:

who|awk '!x[$1]++{print $1}'

Use nawk on Solaris.

6 
perl -ne '$H{$_}++ or print'

remove duplicate without sorting

7 
 who | perl -ane '$H{$F[1]}++ or print'