Bash – awk not doing a new line

awkbashlinuxscripting

I'm trying to print out the users who are currently logged in (each logged in user of each terminal). This is what I currently have:

NOWDATE=$(date +"%Y-%m-%d")
NOWTIME=$(date +"%T")
USERS=$(who | awk -v nd="$NOWDATE"_"$NOWTIME" '{printf nd "\n" " User: "$1" Terminal: "$2" Login: "$3" "$4 "\n"}')

Unfortunately, \n does not work, which means that I can't get a newline after the variable $4. The output doesn't do any new lines. How can I achieve that printf does a new line after the variable $4?

Note: I just perform an echo to list the users, so echo $USERS

Best Answer

Replace

echo $USERS

with:

echo "$USERS"

On unquoted variables, such as in echo $USERS, the shell performs word splitting. That means that all white space characters, such as newline, are replaced by the first character in IFS (by default: a space). If you want to keep your newlines, use double-quotes.

Related Solutions

Linux Users – List Users Created by Current User

There is no record or log kept of which user was responsible for creating each user. Technically, all users are created by root anyway.

Bash – List logged in users (name, terminal, logintime)

Parsing the output of w is probably a better approach than who. Here are some representative data, which shows the login time:

$ who
tom      pts/1        2015-11-15 06:39 (michener:S.0)
$ w
 06:40:10 up  1:04,  1 user,  load average: 0.00, 0.01, 0.05
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
tom      pts/1    michener:S.0     06:39    2.00s  0.03s  0.00s w

Those are more widely available than finger. Since this is a classroom exercise, parsing the data is left to OP. As a hint, awk can do more than print its fields in a one-liner:

Typically, one would handle the output of w by having in the awk script a BEGIN section (to set a line-number or state).
Then, a default action for each line (just curly braces with no pattern) would increment the line number.
Using the line number, handle the first line specially (skip it in this case: OP may need the number of users for a report header, but that is not used in OP's example), and skip the line with USER.
After that, each line can be printed as OP needs. awk will quit when there is no more data; it is not necessary to know the number of users to do this.

If OP is told to use who, that has options to list more information, e.g.,

$ who -l -u
LOGIN    tty5         2015-11-15 05:36              3670 id=5
LOGIN    tty6         2015-11-15 05:36              3671 id=6
LOGIN    tty4         2015-11-15 05:36              3669 id=4
LOGIN    tty3         2015-11-15 05:36              3668 id=3
LOGIN    tty2         2015-11-15 05:36              3667 id=2
LOGIN    tty1         2015-11-15 05:36              3666 id=1
tom      pts/1        2015-11-15 06:39 00:06        5780 (michener:S.0)
tom      pts/2        2015-11-15 06:52   .          6078 (michener:S.1)

again, showing the terminal name and the login times.

Best Answer

Related Solutions

Linux Users – List Users Created by Current User

Bash – List logged in users (name, terminal, logintime)

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