Korn conditional operator not working

Question

I wrote a small korn script, but when I try to run the script, it will not echo the message I want to display. When I try to run it by

ksh script.sh -1

it is not echoing the message.

if [ $# -le 0 ]
    then
        echo "That is a negative integer!"
    exit
fi

Answer 1

In bash/ksh $# represents the number of arguments passed as parameters. What you needed is

if [ ${1:-0} -lt 0 ] # $1 is the first parameter
    then
        echo "That is a negative integer!"
    exit
fi

Or a shorted version of the above

[ ${1:-0} -lt 0 ] && echo "That is a negative integer!" && exit

Edit 1

• I have used shell [ parameter expansion ] ${1:-0} supply a default value.
• Since zero is technically not a negative number, replace -le with -lt

Edit 2

If you're looking forward to match a particular string then do below

[ ${1:-NULL} =  "StringToMatch" ] && DoSomething

If you're looking to see if the output is just has atleast one non-digit character,then do something like below

[[ {1:-NULL} =~  [^[:digit:]]+ ]] && DoSomething

^{Warning : Not all expansions mentioned in the link may not be supported by ksh}