basic comparison-operator question

[DoraC]

Hi,

For some reason I've always thought that to compare numbers in kornshell scripts, you use " -eq ", while for strings you use " == ". In fact, my bolsky/korn book says that the only way to compare strings is with " == ", not " = ", as this is obsolete. However, on our HP UNIX system " == " simply will not work... error messages stating that the == operator was unexpected are returned. " = " does work, however. Some websites advise usage of " -eq " for everything, but this also won't work, as

    if [[ "1" -eq "1.0" ]]
    then
        echo "they are equal as strings...";
    else
        echo "not equal";
    fi;

returns "they are equal as strings...", which is clearly false. I'm confused... is " = " the accepted, non-obsolete string comparison operator, despite what my book claims?

Thanks,
dora

 

[jad]

try "hello" -eq "squiggle" ...

just interested to see the outcome ...

-eq should be used for numeric comparisons.
= should be used for string comparisons.

(so i believe

 

[mrjazz]

Hi Dora,

in Korn Shell the = only works for string comparison:

#!/bin/ksh

[[ "1" = "1.0" ]] && echo "they are equal as strings..." || echo "they are not equal as strings..."

exit 0

You have other string comparing operators like:

!= not equal

= and != are also working with patterns

-n string if the length of the string is not zero

-z string if the length or the string is zero

You can also use > and < for string comparison.

For integer comparison the following operators are correct:

-eq equal

-ne non-equal

-le less than or equal

-lt less than

-ge greater than or equal

-gt greater than

Hope that helps!

mrjazz

 

[DoraC]

Thanks everyone! Your responses were helpful...

dora