Input Parameter Parsing
When a script is called with parameters, you often need to validate them or parse them into named variables. Shell gives you a few common ways to handle this.
Using positional parameters
The simplest way is to read $1, $2, ... directly:
#!/bin/bash
echo "First argument: $1"
echo "Second argument: $2"
Using a default value
You can provide a default when an argument is missing using ${var:-default}:
#!/bin/bash
echo "User: ${1:-guest}"
echo "Home: ${2:-/home/guest}"
Looping over all arguments
Use $@ to iterate over every argument passed:
#!/bin/bash
for arg in "$@"
do
echo "Got: $arg"
done
Counting arguments
$# gives the number of arguments:
#!/bin/bash
echo "Number of arguments: $#"
Exercise
Complete the script so that it prints the second argument passed to it. Call the script with the two arguments apple and banana.
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