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The Linux Command Line

Cover of The Linux Command Line by William E. Shotts Jr. Published by No Starch Press
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Chapter 28. Reading Keyboard Input

The scripts we have written so far lack a feature common to most computer programs—interactivity, the ability of the program to interact with the user. While many programs don’t need to be interactive, some programs benefit from being able to accept input directly from the user. Take, for example, this script from the previous chapter:

#!/bin/bash

# test-integer2: evaluate the value of an integer.

INT=-5

if [[ "$INT" =˜ ^-?[0-9]+$ ]]; then
        if [ $INT -eq 0 ]; then
                echo "INT is zero."
        else
                if [ $INT -lt 0 ]; then
                        echo "INT is negative."
                else
                        echo "INT is positive."
                fi
                if [ $((INT % 2)) -eq 0 ]; then
                        echo "INT is even."
                else
                        echo "INT is odd."
                fi
        fi
else
        echo "INT is not an integer." >&2
        exit 1
fi

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