gistfile1.txt

bash-3.2$ echo $VAR

bash-3.2$ if [ -z $VAR ]; then echo ‘variable is unset’; fi
‘variable is unset’
bash-3.2$ if [ ! -z $VAR ]; then echo ‘variable is set’; fi
bash-3.2$ VAR=''
bash-3.2$ if [ -z $VAR ]; then echo ‘variable is unset’; fi
‘variable is unset’
bash-3.2$ if [ ! -z $VAR ]; then echo ‘variable is set’; fi
bash-3.2$ VAR='test'
bash-3.2$ if [ -z $VAR ]; then echo ‘variable is unset’; fi
bash-3.2$ if [ ! -z $VAR ]; then echo ‘variable is set’; fi
‘variable is set’
bash-3.2$ unset VAR
bash-3.2$ if [ -z $VAR ]; then echo ‘variable is unset’; fi
‘variable is unset’
bash-3.2$ if [ ! -z $VAR ]; then echo ‘variable is set’; fi
bash-3.2$