Check existence of input argument in a Bash shell script

Question

I need to check the existence of an input argument. I have the following script

if [ "$1" -gt "-1" ]
  then echo hi
fi

I get

[: : integer expression expected

How do I check the input argument1 first to see if it exists?

Answer 1

It is:

if [ $# -eq 0 ]
  then
    echo "No arguments supplied"
fi

The $# variable will tell you the number of input arguments the script was passed.

Or you can check if an argument is an empty string or not like:

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

The -z switch will test if the expansion of "$1" is a null string or not. If it is a null string then the body is executed.