Question

I have a question on the test command in the KornShell (ksh). I know -ne is for comparing integers and != is for comparing strings. How will the test command behave if one argument is a string and the other is an integer? I have below conditions in my code and both are working properly.

Code:

myCount=1
myCount=`expr $myCount+ 0`
temp=`ps -aef | grep damn | wc -l`
if [ $temp -ne $myCount]; then
        echo ERROR Number
fi

if [ $temp != $myCount ]; then
        echo ERROR Strings
fi

Output:

ERROR Number
ERROR Strings

Answer 1

The type is not relevant because it’s a simple text substitution. In other words, the value of the variable $temp will be substituted in place of $temp (for example).

At least for the version of ksh I’m running, for the numeric comparison, if the value starts with a non-numeric, it will equate to 0. If it starts with a numeric but contains non-numerics, you will get an error.

For example:

$ export s1=xyz
$ export s2=7xyz
$ export i1=0
$ if [ $i1 -eq $s1 ]
> then
>     echo equal
> fi
equal
$ if [ $i1 -eq $s2 ]
> then
>     echo equal
> fi
ksh: 7xyz: bad number `7xyz'

However, based on your comments, that may not be the case for all versions of ksh.

Based on that, I would try to ensure that you use string comparisons for strings and numeric comparisons for numbers. Anything else may be non-portable.