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Using Linux - bash
I am working on a shell scrip where I ask to input a "whole number". How can make a check to see if the number they input is a whole number? If is not a whole number I will write an error message and send back to "Input a Whole Number".
Just trying to add zero does not really work, as it will produce
syntax error if the input was not an integer.
But then we can use this fact in the following way:
Code:
#!/bin/bash
echo -n "Enter a number: "
read val
haveInteger=0
(test $(($val+0)) == $val)2>/dev/null && haveInteger=1
if [ $haveInteger == 1 ]
then echo Got an integer.
else echo Not an integer.
fi
Integers will pass the test command, but anything else fails
and $haveInteger remains zero.
I got no syntax error in testing my code, unless $VAR is not set, or is an empty string. Can you demonstrate the circumstances in which an error occurs?
Code:
if [ -z $VAR ]
then echo Null string\!
return 1
fi
if [ $(($VAR + 0)) != $VAR ]
then echo Not an integer.
else
echo Integer found.
fi
Ah, very true. I (sadly) did not thoroughly test my code. I had tried begins-with-. decimals (i.e, .12), strings, integers, and nulls, but no >1 decimals.
They have a function to make sure the user inputs a positive whole number. A far easier way to do this is to assume that anything without a decimal is a whole number, and anything with one is not.
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