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Old 10-08-2017, 10:51 PM   #1
Pzykostyle
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How to display the who command output WITHOUT showing the IP address


I'm in an Intro to Linux/UNIX class and I'm having a hard time figuring this one out. I'm being asked to display the students in my class currently logged on but WITHOUT showing the IP address listed at the end of the "who" command.

I've got the initial bit down " who | grep "f132" " but I can't figure that last bit out. I've already tried a few variations of "sed" and "tr" but no luck. Any advice??

ex.

WHAT I GET with " who | grep "f132" ":

f132a12 pts/3 2017-10-08 22:58 (ma.comcast.net)

WHAT I NEED TO SHOW:

f132a12 pts/3 2017-10-08 22:58
 
Old 10-08-2017, 11:30 PM   #2
chrism01
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Well, actually I'd call that a dns address (conventionally IP address means actual digits like 192.168.1.1 )
Anyway, have you considered just using awk (for the whole qn) ?
You could just pipe through 'cut' after your current cmd, but awk can do it all easier.

BTW, when posting code/data/output, please us CODE tags https://www.linuxquestions.org/quest...do=bbcode#code

Last edited by chrism01; 10-09-2017 at 04:17 PM. Reason: typo
 
Old 10-08-2017, 11:34 PM   #3
AnanthaP
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In other words, you want to display only the first 4 columns. Right?

So pass the output of grep (using standard available mechanisms) to a stream editor where you may chop off beyond the fourth column.

ok
 
Old 10-09-2017, 12:16 AM   #4
Turbocapitalist
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You could do it like this with sed if there is always a parenthesis to identify the component to be removed:

Code:
who | sed -r -n -e '/f123a12/{s/ *\(.*$//;p;}'
Though I am sure there is a more elegant pattern to use.

You could do it with awk, too, but that would change the spacing a little.

Last edited by Turbocapitalist; 10-09-2017 at 12:31 AM.
 
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Old 10-09-2017, 01:01 AM   #5
pan64
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you can use sed to remove (anything):
Code:
sed 's/([^()]*)//'
 
Old 10-09-2017, 01:30 AM   #6
MadeInGermany
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Without the -r option a ( is a literal.
A single -e option has no effect (and many -e options are never needed in GNU sed).
Code:
who | sed -n '/f132/{s/ *(.*$//;p;}'
This does a fuzzy match in the whole line including the (hostname) part.

Last edited by MadeInGermany; 10-09-2017 at 01:36 AM. Reason: who cannot do exact match
 
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