Bash nested loop readline from file

Question

I am stuck with the problem. Basically I have two different text files one with questions, another one with answers. Loop reads the first question from the file and waits for input from the user, then compares input with first line in other text file. But it goes thru the whole second file and compares all the lines.

There is a code.

#!/bin/bash

wrong=0
right=0

while  IFS='' read -r question || [[ -n "$question" ]]; 
 do
 echo "$question"
 read input </dev/tty
 while IFS='' read -r answer || [[ -n "$answer" ]];
 do
  if  [[ $answer == *"$input"* ]]
  then
  ((right+=1))
  else
  ((wrong+=1))
 fi
 done < answers.txt
done < file.txt

echo "Wrong answers: $wrong"
echo "Right answers: $right"

What it does at the moment and takes first line from questions, compares with every single line in answers and goes to another question. But I need nested loop only compare with first line and move one to another question and so on.

kojiro · Accepted Answer · 2016-02-19 19:52:48Z

3

Since you're expecting input from a tty, I'm going to assume the files aren't terribly large, memory-wise. Therefore, reading them entirely into memory seems feasible, and a neat way to avoid dealing with the problem you have:

#!/bin/bash

wrong=0
right=0

# Use mapfile to read the files into arrays, one element per line
mapfile -t questions < questions.txt
mapfile -t answers < answers.txt

# Loop over the indices of the questions array
for i in "${!questions[@]}"; do
    question="${questions[i]}"
    [[ $question ]] || continue

    # Look up the answer with the same index as the question
    answer="${answers[i]}"

    # Use read -p to output the question as a prompt
    read -p "$question " input
    if  [[ $answer = *"$input"* ]]
    then
        ((right++))
    else
        ((wrong++))
    fi
done

echo "Wrong answers: $wrong"
echo "Right answers: $right"

edited Feb 19, 2016 at 19:52

answered Feb 19, 2016 at 18:44

kojiro

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5 Comments

Antoshjke Over a year ago

The thing is I need to see a question, then answer it, then it will check an answer from answers.txt and if is right then increment right or if my answer is incorrect then it will increment wrong variable. For example : Question1:........ (first line in questions.txt.) then i input "yes" or "no" then it checks if I am correct going to the first line in answers.txt

Antoshjke Over a year ago

Your code works, but it does not show me a questions.

kojiro Over a year ago

@Antoshjke did you actually try the update? It will output the question.

Antoshjke Over a year ago

Yes I did updated. Trying to change it a little bit. Instead of putting a question in command line, i would like to print it using echo and then wait for an input. But many thanks for it! It did helped a lot!

Timo Over a year ago

How can you extend this example e.g. in that you have 4 answers to each question and not one. I have one file with a question and following 4 answers, please see here. The correct answer will be taken from a list with numbers. So 1,2,4,.. means first answer is number 1, second answer nr. 2, third answer 4, etc. I know the answers and want to show them.

Srinivas Balaji · Accepted Answer · 2016-02-20 12:24:19Z

0

Antoshije, 

You would need to break the loop . try the below

#!/bin/bash

let wrong=0
let right=0


function check_ans
{
in_ans=$1
cat answers.txt | while read ans
do
    if [[ "$in_ans" == "$ans" ]]
        then
        echo "correct"
        break;
    fi
done
}

cat questions.txt | while read question
do
    echo $question
    read ans
    c_or_w=$(check_ans "$ans")
    if [[ $c_or_w == "correct" ]]
    then
        right=$((right+1))
    else
        wrong=$((wrong+1))  
    fi      
done
echo "Wrong answers: $wrong"
echo "Right answers: $right"

edited Feb 20, 2016 at 12:24

answered Feb 19, 2016 at 19:01

Srinivas Balaji

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