Unix Double Test Operator and Relational Operators

Question

In bash scripts,

if [[ $var1 != $var2 ]] 

is equivalent to the form

[ $var1 -ne $var2 ]

Why don't the relational operators (<=, >=) work inside the double test form? I tried [[ $var1 <= $var2 ]] in one of my scripts and it gives me a syntax error. Must I use the form [[ $var1 < $var2 || $var1 = $var2 ]]? Or is there something I'm missing?

Answer 1

You can use the (( )) construct:

$ (( 4 <= 5 )) && echo ok
ok
$ (( 4 <= 3 )) && echo ok || echo ko
ko

or:

var1=4
var2=5
if (( var1 <= var2 )) ; then
   echo ok
fi