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I am testing following code that intends to get input from user and after checking some conditions store it to a new variable. However, this code is not giving me any output or error upon running in the shell terminal. I have given execution permission to the file by sudo chmod +x test.sh.

#!/bin/bash

counter="0"
iso_val="100"

while [ "$counter" == "3" ]
do
    echo -n "Enter ISO [ 100-800 ]: "; read iso
    if (( "$iso" < "100" )) || (( "$iso" > "800" )); then
        echo "Error!"
    elif [ "$iso" == "" ]; then
        echo "Error!"
    else
        iso_val=$iso
        break
    fi
    counter=$[$counter + 1]
done
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  • 1
    You set counter to 0 and then started a while loop which only runs when it's 3. O.o Obviously the loop will never run. Commented Dec 3, 2019 at 4:49
  • I changed it, still no output. counter="1" iso_val="100" while [ "$counter" = "3" ] Commented Dec 3, 2019 at 5:06
  • I am increment in counter also. I don't understand what I am doing wrong here. Can you please correct me where it is wrong. Commented Dec 3, 2019 at 5:07

1 Answer 1

Reset to default
2

Your script as written runs without error and would not produce output.

A quick note: you should temporarily add set -x at the beginning of your bash scripts for getting a good start on debugging.

The issue is the line:

while [ "$counter" == "3" ]

The do block following that line would only be run if $counter was equal to 3, but $counter will not increment unless that do block is ran.

You would need something outside the block you wish to execute to increment your counter. i.e.

#!/bin/bash

counter="0"
iso_val="100"

while [ "$counter" -lt 3 ]
do
    echo -n "Enter ISO [ 100-800 ]: "; read iso
    if [ -z "$iso" ] || [ "$iso" -lt 100 ] || [ "$iso" -gt 800 ]; then
        echo "Error!"
    else
        iso_val=$iso
        break
    fi
    counter=$(($counter + 1))
done

I set a limit to how many times while is ran, otherwise the script does not exit on error. I also changed your string comparisons to integer comparisons where I could.

Edit: New script with clarified requirement from comments, "ask up to three times on error"

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  • Thank you so much for such a nice explanation. Actually, I want to give 3 tries to the user to enter a value, that is why I am using while loop and counter. Commented Dec 3, 2019 at 5:37
  • I made some changes to fit that requirement Commented Dec 3, 2019 at 7:33

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