Validate Inputs in Shell Script

When you create a shell script which requires some parameters as inputs, it is necessary to validate the parameters are recognizable by the script.

• Validate parameter to be a date

  RET=`date -d $1 "+%Y%m%d" 2>/dev/null`
  if [ $? = 0 ]; then
      echo "Input date: [$RET]"
  else
      echo "Invalid date: [$1]"
      exit -1
  fi
  

• Validate parameter to be a number

  RET=`expr match $1 "[0-9]*$"`
  if [ "$RET" -gt 0 ]; then
      echo "Input number: [$RET]"
  else
      echo "Invalid number: [$1]"
      exit -1
  fi
  

• Validate total parameters count

  if [ $# -lt 2 ]; then
      echo "Usage: `basename $0` {PARAM1} {PARAM2} [OPTIONAL_PARAM]
      exit -1
  fi