Shell Programming and Scripting

#!/bin/bash
if [ $# -ne 1 ]; then
    echo Usage: timeon username
    exit 1
fi
if [ $# -eq 1 ]
    then
        user=$1
#    else
#        user=$USER
fi
# check if the user exists on Matrix
a=$(ypcat passwd | grep -w ^$user)
if [ "$a" == "" ]
    then
        echo "$user does not exist on Matrix, try again." >&2
        exit 2
elif [ "$a" != "" ]; then
        # get the username
        username=$(echo $a | cut -d: -f1)
        echo Username:    $username
fi
# Check for existing /tmp/tst folder
if [ "/tmp/tst" != "" ]; then
rm -rf /tmp/tst
# Make a directory in /tmp called tst
mkdir -p /tmp/tst
fi
# Copy wtmp files in /tmp/tst folder and unzip them:

cd /tmp/tst                     # safe place to work
tfile=/tmp/tst/wtmp.$$          # temp file to uncompress into
big_file=/tmp/tst/$USER.wtmp    #collect all output from wtmp into one file

ls /var/log/wtmp*bz2 | while read file    # for each wtmp file
do
    bunzip2 -dc $file >$tfile   # uncompress writing output to tmp file
    last -F -a -f $tfile        # run last on it
done >$big_file                 # save all output from last in one file
last -F -a >>$big_file          # append formatted output from current wtmp
rm $tfile                       # tmp file not needed

### parse your big file (/tmp/$USER.wtmp) here #####

# cleanup before exit
#rm $big_file
b=$( cat /tmp/tst/$USER.wtmp | grep $user )
echo $b

# your script as you have it up to here....
# cleanup before exit
#rm $big_file

grep $user  /tmp/tst/$USER.wtmp | awk '
    /wtmp begins/ { next; }
    /still logged in/ { next; }
    $0 == reboot { next; }

    NF > 0  {
        if( NR > 1 )
            printf( "\n" );

        printf( "       User:\t%s\n", $1 );     # user
        printf( "      Start:\t%s %s %s %s\n", $3, $4, $5, $6 );
        if( $9 == "down" )
            printf( "        End:\tshutdown\n" );
        else
            printf( "        End:\t%s %s %s %s\n", $9, $10, $11, $12 );

        if( substr( $NF, 1, 1 ) == "(" )
        {
            t = $NF;
            h = "localhost";
        }
        else
        {
            t = $(NF-1);
            h = $NF;
        }

        gsub( "[()]", "", t );
        printf( "    Time On:\t%s\n", t );
        printf( "Remote Host:\t%s\n", h );
} '

grep $user /tmp/$USER.wtmp| while read  uname tty st_dow st_mon st_day st_time st_yr junk end_dow end_mon end_day end_time end_yr ttime host
do
    case $end_dow in
        crash|gone|down|still) ;;       # ignore those with missing info
        *)
            printf "\n"
            printf "       User:\t%s\n" $uname
            printf "      Start:\t%s %s %s %s\n" $st_dow $st_mon $st_day $st_time
            printf "        End:\t%s %s %s %s\n" $end_dow $end_mon $end_day $end_time
            printf "    Time On:\t%s\n" $ttime
            printf "Remote Host:\t%s\n" ${host:-localhost}
        ;;
    esac
done