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+    #!/bin/bash -e
+    #For course FYD500, exam 2020
+    #No warranty provided
+    
+    # Price checker for imaginary items, has fake discount for elderly.
+    #   CTRL+C (SIGINT) enters admin mode which shows some host information,
+    #   assuming the correct password is supplied (read from file techpasswd)"
+    
+    ### PROVIDED FUNCTIONS ###
+    function user_mode {
+        #terminal location provided by customer
+        LOCATION=$1
+        OPTION_1="Price Information"
+        OPTION_2="Senior Rebate"
+    
+        echo "
+            1) $OPTION_1
+            2) $OPTION_2"
+    
+        #select output gets sent to stderr for some reason?
+        select OPTION in "$OPTION_1" "$OPTION_2"
+        do
+            case $OPTION in
+                "$OPTION_1")
+                    price_info
+                    ;;
+                "$OPTION_2")
+                    senior_rebate
+                    ;;
+                *)  ;;
+            esac
+        done
+    }
+    
+    function price_info {
+        while :
+        do
+            echo -e "Enter an article number: "
+            read  ARTICLE
+    
+            #article code length (includes '\n')
+            let ARTICLE_LEN="$(echo "$ARTICLE" | wc -m )"
+            if [ ! $ARTICLE_LEN -eq "8" ]; then
+                echo "Invalid length of article code"
+                echo "Expected 7, got $ARTICLE_LEN" 1>&2
+                echo
+                continue
+            fi
+    
+            LOCATION_CODE="${ARTICLE:0:1}"
+            PRICE_CODE="${ARTICLE:1:5}"
+            CHECKSUM="${ARTICLE:6:6}"
+    
+            #Check if item location matches store location
+            ERROR=0
+            PRICE_MULTIPLIER="1"
+            if [ "$LOCATION" = "G" ]; then
+                if [ ! "$LOCATION_CODE" = "1" ]; then ERROR=1; fi
+            elif [ "$LOCATION" = "S" ]; then
+                #Stockholm tax
+                PRICE_MULTIPLIER="1.15"
+                if [ ! "$LOCATION_CODE" = "2" ]; then ERROR=1; fi
+            elif [ "$LOCATION" = "M" ]; then
+                if [ ! "$LOCATION_CODE" = "3" ]; then ERROR=1; fi
+            else
+                ERROR=1
+            fi
+    
+            if [ "$ERROR" -eq "1" ]; then
+                echo "Invalid location article code combination!"
+                continue
+            fi
+    
+            #checksum should be sum of digits modulus 7
+            EXPECTED_CHECKSUM=$(echo "$PRICE_CODE" |\
+                awk 'BEGIN{FIELDWIDTHS="1 1 1 1 1"}{print ($1+$2+$3+$4+$5)%7}')
+    
+            if [ ! $CHECKSUM -eq $EXPECTED_CHECKSUM ]; then
+                echo "Invalid checksum!" 1>&2 #error
+                echo -e "Invalid article\n"
+                continue
+            fi
+    
+            case "$PRICE_CODE" in
+                "64964")
+                    PRICE=$(awk "BEGIN {print 120*${PRICE_MULTIPLIER}}")
+                    echo -e "$ARTICLE (USB stick): $PRICE kronor\n"
+                    ;;
+                "59457")
+                    PRICE=$(awk "BEGIN {print 400*${PRICE_MULTIPLIER}}")
+                    echo -e "$ARTICLE (headset): $PRICE kronor\n"
+                    ;;
+                *)
+                    echo -e "Hm, well I can't seem to find the product ($ARTICLE) in our system!\n"
+                    ;;
+            esac
+        done
+    }
+    
+    function senior_rebate {
+        BIRTHDAY=""
+    
+        #Require 8 chars AND all digits
+        while [ ! ${#BIRTHDAY} -eq 8 ] || [ ! -z "${BIRTH_YEAR##*[!0-9]*}" ]
+        do
+            echo -e "Enter your birthday (YYYYMMDD)"
+            read BIRTHDAY
+        done
+    
+        CURRENT_DATE=$(date +"%Y%m%d")
+        let AGE=$CURRENT_DATE-$BIRTHDAY
+        #Age in years
+        AGE=${AGE:0:2}
+    
+        if [ $AGE -gt 64 ]; then
+            echo "CONGRATULATIONS YOU ARE SENIOR REBATE ELIGABLE!"
+        else
+            echo "Good try kid, come back later"
+        fi
+    }
+    
+    function tech_mode {
+        #ignore SIGINT signals
+        trap "" SIGINT
+        #Reset errors to tty
+        exec 2>/dev/tty
+        #Errors and warnings goes to both TTY and file
+        exec > >(tee admin.log)
+    
+        FILE="techpasswd"
+    
+        if [[ ! -f "$FILE" ]]; then
+            echo "ERROR: password file not found" 1>&2
+            sleep 10
+            return
+        fi
+    
+        echo "Enter secret password:"
+        read PASSWORD
+    
+        if [ "$PASSWORD" = "$( cat $FILE )" ]; then
+            echo "CPU Model: $(  lscpu | awk -F:  '/Model name/ { print $2 }' | sed 's/^ *//g'  )"
+    
+            echo "Processes over 5000kB RSS: $(ps -eo rss --sort=-rss | awk '{ if ( $1 > 5000 ) {sum+=1}} {print sum}' | tail -n 1)"
+    
+            echo "System was last updated: $( stat /etc/redhat-release | awk '/Modify/ { print $2 " " $3 " (" $4 ")" }' )"
+    
+        else
+            echo "Incorrect password" 1>&2
+            sleep 10
+        fi
+    
+        return
+    }
+    
+    function help {
+        echo -e "\\033[1m${0}\\033[0m usage:
+        \\e[0;31m-h\\e[0m             Prints this help
+        \\e[0;31m-shop G/S/M\\e[0m    Enter shop by specifying city Gothenburg, Stockholm, Malmo. Exactly one additional argument is required G, S, or M.
+    
+        Any other input will result in the printing of this help screen."
+    }
+    
+    
+    ### PROGRAM STARTS HERE ###
+    
+    #Hide errors from user, send to log file
+    exec 2>file.log
+    
+    #CTRL+C triggers admin mode (requires password)
+    trap "tech_mode" SIGINT
+    
+    #0-1 arguments always shows help
+    if [ $# -lt 2 ]; then
+        help
+    #2 arguments check whether user wants to enter shop
+    elif [ $# -eq 2 ]; then
+        case $1 in
+            "-shop")
+                user_mode $2
+                ;;
+            *)
+                help
+                ;;
+        esac
+    #Too many arguments show help
+    else
+        help
+    fi