Shell Programming and Scripting

Hi guys!

Just was wanting to run a command that would allow me to seperate the currently logged in users.

Basically from this format:

Code:

 
user1
user2
user3

To:

Code:

user1|user2|user3

(Note the lack of a pipe at the end, not sure if thats possible)

Basically it needs to be in this format for grep -E to use them as a pattern.

I'm using cut to get the usernames,

Code:

who | cut -f1 -d " "

Just wanted to know if there is an easy way to do this?

Thanks,

-Crawf

Why don't you just use who | cut -f1 -d " " | fgrep -f - somefile

Good idea, but i'm not wanting to really output to a file thats all..

Just to give you an idea of exactly what im trying to do, is i'm trying to write a script to check if a user has logged in multiple times. If found, is then checked and matched with a text file of usernames who are not allowed to have multiple logins.

So far:

Code:

while true
do
if [ $(grep -c -w -E 'user1|user2' user.deny) -gt 1 ] ; then
grep -w -E 'user1|user2' user.deny
else
echo "none"
fi
sleep 3
done

Obviously the problem here is that it doesnt check the currently logged in users, which would be from the cut command mentioned earlier. I guess i'm just having trouble joining those two things up, or am i going about it the wrong way?

Any help would be appreciated!

-Crawf

try this :

Code:

who | cut -f1 -d " " | tr "\n" "|" | egrep - user.deny

who |awk '{print $1}'|paste -d"|" -s -

Code:

while true; do
  if ! who | cut -f1 -d " " | uniq -d | fgrep -xf user.deny; then
    echo none
  fi
  sleep 3
done

Era, that seems to have solved the problem! The key to that was the uniq -d command i think, i didnt even know what the did until looking it up in the man pages.

What is the different between using fgrep and grep? I assume fgrep is faster/more efficient?

Thanks to the others for your reply's as well! Solutions worked, but era's code allows you to not have to add pipes between usernames. Handy!

Thanks again!

-Crawf