Gfrktyl

Classically, the command is 'who' rather than 'users', but 'who' gives you more information. Looking back at the original Unix articles (mid-70s), the example would have been:

who | wc -l

Using 'wc -l' counts lines of output - it works with both 'users' and 'who'. Using '-w' only works reliably when there is one word per user (as with 'users' but not with 'who').

You could use 'grep -c' to count the lines. Since you are only interested in non-blank user names, you could do:

who | grep -c .

There's always at least one character on each line.

As noted in the comments by John T, the users command differs from who in a number of respects. The most important one is that instead of giving one name per line, it spreads the names out several per line — I don't have a machine with enough different users logged in to test what happens when the number of users becomes large. The other difference is that 'who' reports on terminal connections in use. With multiple terminal windows open, it will show multiple lines for a single user, whereas 'users' seems to list a logged in user just once.

As a consequence of this difference, the 'grep -c .' formulation won't work with the 'users' command; 'wc -w' is necessary.

Open a shell and type:

who -q

The last line will give you a count.

EDIT:

(sigh) I misunderstood the question. Here's a somewhat brute-force approach:

To see unique user names:

who | awk '{ print $1 }' | sort | uniq

To see a count of unique users:

who | awk '{ print $1 }' | sort | uniq | wc -l 

Do you want to see the number of sessions, or the number of actual users?

$ who

andrew   tty1         2009-07-26 15:31 (:0)

andrew   pts/0        2009-07-27 00:11 (:0.0)

andrew   pts/1        2009-07-27 01:58 (:0.0)

That's on my laptop, so i'm the only user, but i'm logged on three times.

$ who | wc -l

3

$ users | wc -w

3

It is fairly easy to filter out these duplicates though to get the number of actual users.

$ users | tr ' ' 'n' | sort -u 

andrew

$ users | tr ' ' 'n' | sort -u | wc -l

1

Here's a bash version of tink's great awk post:

set $(users)

declare -A user

for u ; do ((user[$u]++)) ; done

for key in "${!user[@]}" ; do echo "$key: ${user[$key]}" ; done | column -t | sort -nk 2

Ok, it's a little bit longer, but was worth finding this one ... :).

While testing, do before next attempt:

shift $#                # clear positional parameters

unset user              # remove associative array variable

number of the users currently logged in:

who |cut -c 1-9 |sort -u |wc -l

the above buta with their account name:

who |cut -c 1-9 |sort -u |tee /dev/tty |wc -l

who | cut --delimiter=' ' -f 1 | sort -u | wc -l

Who prints out the list, cut removes everything but the first row, sort -u sort it and removes duplicates and wc -l counts the lines. Works fine for me on ubuntu/bash :)

You can simply use w (/usr/bin/w on my Red Hat based system) or uptime, they show the actual number of logged in users.

w:

                              v

 22:40:38 up 3 days, 22 min,  1 user,  load average: 0.02, 0.01, 0.00

USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT

manuel   pts/0    pc-manuel        09:35    0.00s  0.07s  0.00s /usr/bin/screen -xRR

uptime:

                              v

 22:39:18 up 3 days, 21 min,  1 user,  load average: 0.08, 0.02, 0.01

And a method that uses only one pipe...

users | awk '{for(i=1;i<=NF;i++){a[$i]++}}END{for(i in a){print i"t"a[i]}}'

:}

http://www.gnu.org/software/coreutils/manual/html_node/who-invocation.html

"who" prints information about users who are currently logged on. Synopsis:

who [option] [file] [am i]

You could always download the free tool for unix called TOP. It produces a list of the users and also what they are doing on the system at the time and will continue to update as long as it is running.

It is located at http://www.unixtop.org/

It has many command line switches so you should be able to extract the information you are looking for.

who | cut -d ' ' -f1 | uniq | wc -l

If you are looking for the total number of users logged in and logged off in a proper sequence, the best command to run is

cat -n /etc/passwd