bash if check function parameter value code example

Example 1: verify parameter one bash

if [ -z "$1" ]
  then
    echo "No argument supplied"
fi

Example 2: check if variable is a number in bash

re='^[0-9]+$'
if ! [[ $yournumber =~ $re ]] ; then
   echo "error: Not a number" >&2; exit 1
fi