Check if parameter is NULL (shell scripting)

[theory]

Hello,

Im really new to shell scripting and I'm trying to make a recursive algorithm, but I'm having difficulty in making a check to see wether a parameter has a value or not.

if [ $1 -eq NULL ] && [ $2 -eq NULL ]
then
echo "Parameters doesn't have a value ($1 and $2)"

else echo "$1 and $2 has a value or check failed"
exit 1
fi

Btw, im guessing theres differences when writing to a Kourne or Bash shell. I'd like it to work under ksh, but if it can only be done under bash then fine! :-)

Cheers in advance

[BlueC]

perhaps....

if [ -n "$1" ] && [ -n "$2" ] # note the quoted test strings
then
  echo "Strings \"$1\" and \"$2\" are not null."
else  
  echo "Strings \"$1\" and \"$2\" are null."
fi

alternatively:

if [ $1 ] && [ $2 ]
then
  echo "Strings \"$1\" and \"$2\" are not null."
else  
  echo "Strings \"$1\" and \"$2\" are null."
fi

For more see http://tldp.org/LDP/abs/html/comparison-ops.html

HTH

[theory]

They both work.

Thank you very much :-)