On a bash script, I personally like to use the following script to set parameters:
#!/bin/bash
helpFunction()
{
echo ""
echo "Usage: $0 -a parameterA -b parameterB -c parameterC"
echo -e "\t-a Description of what is parameterA"
echo -e "\t-b Description of what is parameterB"
echo -e "\t-c Description of what is parameterC"
exit 1 # Exit script after printing help
}
while getopts "a:b:c:" opt
do
case "$opt" in
a ) parameterA="$OPTARG" ;;
b ) parameterB="$OPTARG" ;;
c ) parameterC="$OPTARG" ;;
? ) helpFunction ;; # Print helpFunction in case parameter is non-existent
esac
done
# Print helpFunction in case parameters are empty
if [ -z "$parameterA" ] || [ -z "$parameterB" ] || [ -z "$parameterC" ]
then
echo "Some or all of the parameters are empty";
helpFunction
fi
# Begin script in case all parameters are correct
echo "$parameterA"
echo "$parameterB"
echo "$parameterC"
With this structure, we don't rely on the order of the parameters, as we're defining a key letter to each one of them. Also, the help function will be printed all the times that the parameters are defined wrongly. It's very useful when we have a lot of scripts with different parameters to handle. It works as the following:
