UNIX for Dummies Questions & Answers

[ $a == $b ] does seem to work on solaris but it's not general. It fails on hp-ux too. Use
[ $a = $b ]

But be aware that this is a string compare.
a=1
b=1.0
[ $a = $b ] will be false

I reformulate my question because that I say is not clear.

a=1
b=1.75 or 1,75

if [ $a -lt $b ]
then echo " It is normal 1 < 1,75"
else echo "ANOMAL"
fi

And I want this message: "It is normal 1,75 > 1"

Castelior, the ksh supplied with AIX does not have support for any non-integer arithmetic. It can't add or subtract or even compare them. So you will have to do everything using other programs. If a is less than b, then the expression a-b will be negative. Negative numbers will have a minus sign as the first character.
a=1
b=1.75
c=$(echo $a - $b | bc)

if [[ $c = -* ]] ; then

OK! It's a good idea!

Thanks a lot Perderabo and pressy