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Full Discussion: Bourne Shell - Problem with while loop variable scope.
Top Forums Shell Programming and Scripting Bourne Shell - Problem with while loop variable scope. Post 302476428 by DaveRich on Wednesday 1st of December 2010 04:04:27 PM
Old 12-01-2010
Bourne Shell - Problem with while loop variable scope.
Hello

I am having issues with a script I'm working on developing on a Solaris machine.

The script is intended to find out how many times a particular user (by given userid) has logged into the local system for more than one hour today.

Here is my while loop:
Code:
last $user | grep -v 'sshd' | grep -v 'still logged in' | grep "`date | cut -d' ' -f2-4`" | cut -d\( -f2 | cut -d: -f1 | while read numHours
do
        if [ $numHours -gt 0 ]; then
                numLogins=$(( $numLogins + 1 ))
                echo "$user logged in once for more than an hour ($numHours hours)." #DEBUG
        fi
done

I have declared numLogins before the loop, and the problem is after the loop I try and "echo $numLogins" but numLogins always contains 0. Even when my debug line prints out showing that the user has logged in for at least an hour.

I have determined that I believe this is because the while loop (when used in a pipeline) has a seperate variable scope, but I have tried rewriting my loop like:

Code:
while loop=read $line
do
        numHours=`echo $line | grep -v 'sshd' | grep -v 'still logged in' | grep "\`date | cut -d' ' -f2-4`" | cut -d\( -f2 | cut -d: -f1
        if [ $numHours -gt 0 ]; then
                numLogins=$(( $numLogins + 1 ))
                echo "$user logged in once for more than an hour ($numHours hours)." #DEBUG
        fi
done < `last $user`

I also thought it may be with the way I was incrementing my numLogins variable,
I have tried to use:
Code:
(( numLogins++ ))
using expr,
numLogins=`echo $numLogins + 1 | bc`

and a few other methods I can't quite remember.

Any help on this would be extremely appreciated.
Thanks a lot!
Last edited by DaveRich; 12-01-2010 at 05:10 PM..
 

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LEARN ABOUT HPUX

rwho

rwho(1) 						      General Commands Manual							   rwho(1)

NAME

       rwho - show who is logged in on local machines

SYNOPSIS

DESCRIPTION

       produces  output  similar  to the output of the HP-UX command for all machines on the local network that are running the daemon (see who(1)
       and rwhod(1M)).	If has not received a report from a machine for 11 minutes, assumes the machine is down and does  not  report  users  last
       known to be logged into that machine.

       output  line  has  fields for the name of the user, the name of the machine, the user's terminal line, the time the user logged in, and the
       amount of time the user has been idle.  Idle time is shown as:

       If a user has not typed to the system for a minute or more, reports this as idle time.  If a user has not typed to the system for  an  hour
       or more, the user is omitted from output unless the flag is given.

       An example output line from would look similar to:

       This  output  line  could  be  interpreted as is logged into and his terminal line is has been logged on since September 12  at 13:28 (1:28
       p.m.).  has not typed anything into for 11 minutes.

WARNINGS

       output becomes unwieldy when the number of users for each machine on the local network running becomes large.  One line	of  output  occurs
       for each user on each machine on the local network that is running

AUTHOR

       was developed by the University of California, Berkeley.

FILES

       Information about other machines.

SEE ALSO

       ruptime(1), rusers(1), rwhod(1M).

																	   rwho(1)
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