Set default value script/function parameter (Bash)

$1, $2 .. $n can be used to retrieve parameters passed to Bash scripts or functions. Default values can be assigned to these variables without the use of [ -z $n ] && ... in the following syntax:

${n:-default}

Where:

• n The parameter index value
• default The value that should be assigned if it is null/not set.

Example

To create a error handling function in a script that gives a exit code of 1 if it is not set under $2:

fatal()
{
        exitval=${2:-1}
        echo `date`" - FATAL - $1"
        exit $exitval
}

Category:Linux Category:Bash