Eternal bash logging

bash_eternal_history.sh

#!/bin/bash
function log_cmd                                                                                                                                                                                                
{                                                                                                                                                                                                               
    local mytty=$(tty | sed 's/\/dev\///')                                                                                                                                                                      
    local host=$(who | grep "$mytty " | sed 's/^.*(\(.*\)).*$/[\1]/')                                                                                                                                           
    local user=$(ls -l /dev/${mytty} | awk '{print $3}')                                                                                                                                                       
                                                                                                                                                                                                                
    HISTORY="$(history 1)"                                                                                                                                                                                      
    if [ "z$HISTORY" != "z" ];                                                                                                                                                                                  
    then                                                                                                                                                                                                        
        if [ "$HISTORY" != "$LASTHISTORY" ];                                                                                                                                                                    
        then                                                                                                                                                                                                    
            echo "$(date +%Y%m%d-%H%M%S) $user $mytty $host::" "$HISTORY"   >> ~/.bash_eternal_history                                                                                                          
        fi                                                                                                                                                                                                      
    fi                                                                                                                                                                                                          
    export LASTHISTORY="$HISTORY"                                                                                                                                                                               
}                                                                                                                                                                                                               
trap "log_cmd 2>/dev/null" DEBUG