variables in shell script is not calculated correctly-CodePudding

What is the mistake in my below shell script:

#!/bin/bash

total=0

for i in 1 2 3 4
do
    echo -n "Enter Passenger Name: "
    read pname
    
    echo -n "Enter Car Number: "
    read ncar

    echo -n "Enter Amount: "
    read amount

    echo -n "Enter Distance Travelled: "
    read dtravelled

    total=$((total   dtravelled))

    average=$(echo "$total 4" | awk '{print $1/$2}')

    if test $dtravelled -gt 10000 -a $dtravelled -le 7000
    then
        bpassenger=$((business_pass   1))
    elif test $dtravelled -gt 7000 -a $dtravelled -le 5000
    then
        lpassenger=$((leisure_pass   1))
    else
        opassenger=$((other_pass   1))
    fi

    if test $i -eq 1
    then
        lname=$pname
        low=$dtravelled
    fi

    if test $dtravelled -lt $low
    then
        lname=$pname
        low=$dtravelled
    fi
    
    echo
done

echo "Total of distance travelled by the passengers: $total"
echo "Average distance travelled by the passengers: $average"
echo "Number of business passengers: $bpassenger"
echo "Number of leisure passengers: $lpassenger"
echo "Number of other passengers: $opassenger"
echo "lowest distance travelled is $low by $lname."

***the below block is not calculated *** I always get empty output on this calculation

if test $dtravelled -gt 10000 -a $dtravelled -le 7000
        then
            bpassenger=$((business_pass   1))
        elif test $dtravelled -gt 7000 -a $dtravelled -le 5000
        then
            lpassenger=$((leisure_pass   1))
        else
            opassenger=$((other_pass   1))
        fi

output:

bash mySript.sh

Enter Passenger Name: ahmad
Enter Car Number: 9889
Enter Amount: 20
Enter Distance Travelled: 1100

Enter Passenger Name: sara
Enter Car Number: 5214
Enter Amount: 300
Enter Distance Travelled: 1120

Enter Passenger Name: mohammad
Enter Car Number: 9713
Enter Amount: 6
Enter Distance Travelled: 500

Enter Passenger Name: nora
Enter Car Number: 98765
Enter Amount: 41
Enter Distance Travelled: 7500

Total of distance travelled by the passengers: 10220
Average distance travelled by the passengers: 2555
***Number of business passengers:*** 
***Number of leisure passengers:*** 
Number of other passengers: 1
lowest distance travelled is 500 by mohammad.

CodePudding user response：

When writing test $dtravelled -gt 10000 -a $dtravelled -le 7000 in normal mathematical notation, you see that it can never be true:

dtravelled > 10000 and dtravelled < 7000
⇔ 10000 < dtravelled < 7000
⇒ 10000 < 7000
⇒ False

Same for the other test with 7000 and 5000.

Adapt your logic. If you run into problems again, add set -x to the beginning of your script or execute it with bash -x scriptFile.sh. This will print the executed statements and variable contents, which will make debugging easier.

CodePudding user response：

I believe you can find everything in this line of code:

total=$((total   dtravelled))

... which should become:

total=$(($total   $dtravelled))

When you assign a variable, then you just put the name of the variable at the left side of the equal-sign:

var=...

When you use the value of a variable, which you do a the right side of the equal-sign, you must add a dollarsign:

...=...$var...