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.