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28 – Reading Keyboard Input
The scripts we have written so far lack a feature common in most computer programs — interactivity. That is, the ability of the program to interact with the user. While many pro- grams 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 [ $((INT % 2)) -eq 0 ]; then echo "INT is even."
else
echo "INT is odd."
fi
fi else
echo "INT is not an integer." >&2 exit 1
fi
#!/bin/bash
# test-integer2: evaluate the value of an integer.
INT=-5
if [[ "$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
Each time we want to change the value of INT, we have to edit the script. It would be much more useful if the script could ask the user for a value. In this chapter, we will be- gin to look at how we can add interactivity to our programs.