handling blank iputs in a shell script.

Here is simple script to handle blank inputs in your interactive shell scripts.

#!bin/sh
while :
echo "enter value for a:";read -r a;  do
         if [ -z "${a}" ]; then
         echo "That was empty, do it again!"

        else ## echo "Checking now..."
                echo "value passed is :$a"
                echo "valid input received."
                break
    fi
done

echo "We are out of loop:"

Sample Output :

[Linux01] $ . Test_input11.sh
enter value for a:

That was empty, do it again!
enter value for a:

That was empty, do it again!
enter value for a:

That was empty, do it again!
enter value for a:
1
value passed is :1
valid input received.
We are out of loop:

Error handling in shell script

Error handling in shell script while receiving user input

 
This is help full sample script that can help in error handling.In situations where I give user to choose 1 or 2 but lets say in rush/hurry user inputs a diff value. This script can handle those situations. In below script the user will be in loop until he passes a expected value (1 or 2 in this case). This script can be altered as per your requirement.

On how to handle just blank inputs use this link

-- Script starts here

#!bin/sh
## Created by     :    Arvind Toorpu
## This script will prompt user for input until the user passes the expected input.
##
while :
echo "enter value for a:";read -r a;  do
         if [ -z "${a}" ]; then
         echo "That was empty, do it again!"

        elif [ "${a}" -eq "1" ]  || [ "${a}" -eq "2" ]; then
                ## echo "Checking now..."
                echo "value passed is :$a"
                echo "Condition success"
         break

        elif [ "${a}" -ge "3" ]
        then
        echo "Select either option :1 or :2 "
    fi
##break
done


Sample output :

atoorpu@Linux01:[~/TEST_DIR/scripts] $ . Test_input2.sh
enter value for a:

That was empty, do it again!
enter value for a:

That was empty, do it again!
enter value for a:
4
Select either option :1 or :2
enter value for a:
5
Select either option :1 or :2
enter value for a:
6
Select either option :1 or :2
enter value for a:
6
Select either option :1 or :2
enter value for a:
7
Select either option :1 or :2
enter value for a:
2
value passed is :2
Condition success
do your thing here with read value 2