input-args.sh

echo "amount of arguments:" $#
echo "values:" $@
echo "first argument" ${1}
echo "last argument" ${!#}

# default value or value from env variable
export env_param_value="some value "
unset env_param_value
[[ -z $env_param_value ]] && my_param="default_value" || my_param=$env_param_value
echo $my_param


# check return value 
if [[ 1 -eq "$?" ]]; then echo "error"; else echo "done"; fi
if [[ "$1" == `echo "test"` ]];then echo "working"; fi


if [[ $# -gt 3 ]] || [[ $# -eq 0 ]];then
   echo "Either 0 or more than 2 input arguments are expected"
   exit 1
fi

if [[ $# != 3 ]]
then
    echo " 3 input parameters expected"
fi

# check existence for input parameter #2 
# if [ ! -n "$2" ]
if [ -z "$2" ]
then
  echo "two input parameters are expected: digit and string "
  exit 1
fi  

param_1=$1
param_2=$2

echo $param_1
echo $param_2

# check input parameters to be in ranges
if [[ $param_1 -gt 0 && $param_1 -lt 25 ]] 
then
  echo "first argument is positive 0..25"
elif [ $param_1 -ge 25 ] && [ $param_1 -lt 100 ]
then 
  echo "first argument is positive and Greater Than 25"
else
  echo "negative"
fi

echo "---"
# arifmetic operations
param_1_3=$(( $param_1 + $param_1 + $param_1 ))
echo "summarize: "$param_1_3
echo " multiply: "$(( $param_1 * $param_1 * $param_1 ))
echo "   divide: "$(( $param_1 * $param_1 * $param_1 / 2 ))
echo "      mod: "$(( $param_1 * $param_1 * $param_1 % 2 ))

echo "---"
# length of the string
param_2_len=`echo $param_2 | awk '{print length($0)}'`
echo "param_2 lenght is: "$param_2_len

counter=13
while [ $counter -ge 0 ]
do
  counter=$(( counter-1 ))
  printf ".%d" $counter
done