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Shell Script to Validate Integer Input

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  • Difficulty Level : Medium
  • Last Updated : 09 Apr, 2021
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Here we are going to see a shell script which validates an integer. We are going to display whether the input entered is an integer or an invalid input. 


  1. Take input from the user.
  2. Store the input of any variable
  3. Now we are going to trim the input in such a way that all the -(minus) or +(plus) signs before the input are trimmed down.
  4. Now we are going to apply a regular expression to check if the input pattern has multiple occurrences of digits 0-9.
  5. If the input pattern contains only digits, this means that the input entered is a valid integer and in all other cases, invalid integer input is shown.

The Shell Script is given below:

# Asking the user to enter an input
echo "Enter an input"

# reading and storing input
read variable

# Applying the approach given above

case ${variable#[-+]} in
  *[!0-9]* | '') echo "Not an integer" ;;
  * ) echo "Valid integer number" ;;


Shell Script to validate integer input, allow negative integers too

Output of the above code snippet

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