Check whether input is an integer and equal to a specific number in bash

Question

Trying to check whether or not a value entered by a user is an integer, as well as equal to 35 or 75. If the value entered is an integer and equal to 35 or 75, then I wish to inform the user of this. If the entered value is anything other than 35 or 75 (e.g. a string, null or different integer) then I aim to let the user know it's not valid and for them to try again.

read -p 'Please enter an integer that is either equal to 35 or equal to 75: ' value

if [ $value =~ ^[0-9]+$ ] && ([ $value -eq 35 ] || [ $value -eq 75 ]
    echo "The input is acceptable"
    exit 1

else
    echo "The value is invalid. Try again."

fi

exit 0

The error I keep receiving is line 10: syntax error near unexpected token 'else'

You're missing a closing parentheses. And the first condition should be wrapped in double brackets; single ones don't support regex. — oguz ismail
– oguz ismail, Commented Mar 22, 2021 at 12:01
@NigelWash: Complementing the correct commen of oguz ismail: Have a look at man test to see what is allowed within single brackets. — user1934428
– user1934428, Commented Mar 22, 2021 at 14:17

Thomas Hansen · Accepted Answer · 2021-03-22 13:15:27Z

1

You were missing a then. I would tidy up like this:

#!/bin/bash

read -r -p 'Please enter an integer that is either equal to 35 or equal to 75: ' value

if [[ "$value" =~ ^[0-9]+$ ]] && [ "$value" -eq 35 ] || [ "$value" -eq 75 ]
    then
    echo "The input is acceptable"
    exit 0

else
    echo "The value is invalid. Try again."

fi

exit 0

Update: In order to keep prompting the user for input, do something along these lines:

#!/bin/bash

while 
  read -r -p 'Please enter an integer that is either equal to 35 or equal to 75: ' value
do
if [[ "$value" =~ ^[0-9]+$ ]] && [ "$value" -eq 35 ] || [ "$value" -eq 75 ]
    then
    echo "The input is acceptable"
    exit 0
else
    echo "The value is invalid. Try again."

fi
done

exit 0

edited Mar 22, 2021 at 13:15

answered Mar 22, 2021 at 12:09

Thomas Hansen

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1 Comment

Nigel Wash Over a year ago

Hi Thomas, thanks a lot for the help! Is there a way to create a while loop that keeps prompting the user until the numbers 35 or 75 have been entered?

Oliniusz · Accepted Answer · 2021-03-22 12:13:26Z

1

Not sure about the exit 1 when the answer is correct, I guess you wanted to do something like that:

#!/bin/bash

read -p 'Please enter an integer that is either equal to 35 or equal to 75: ' value

if [[ $value =~ ^[0-9]+$ && ($value -eq 35 || $value -eq 75) ]]; then
  echo "The input is acceptable"
else
  echo "The value is invalid. Try again."
  exit 1
fi

exit 0

I would personally simplify it to:

#!/bin/bash

read -p 'Please enter an integer that is either equal to 35 or equal to 75: ' value

if [[ "${value}" == "35" || "${value}" == "75" ]]; then
  echo "The input is acceptable"
else
  echo "The value is invalid. Try again."
  exit 1
fi

exit 0

answered Mar 22, 2021 at 12:13

Oliniusz

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