Shell Script logical operator for conditions

Question

 $i="500,600"
 $j="600"

 if[$i -ne $j]; then
    #some line
 else
    #some line
 fi

This if condition is not going inside.

this if condition fails. else is pass.

how is this possible

can someone help me on this

Answer 1

The trick is to consider the "[" sign as a command (in fact it is one indeed), whose last argument must be a "]". So you must ensure that there is a space after [ and all of its arguments go to the proper place. In your case:

if [ "$i" -ne "$j" ]
 then
     # some code
 else
     # some code
fi

Since [ is a command, you might want to omit the if structure and use logical operators, taking advantage of lazy evaluation. The following means the same:

[ "$i" -ne "$j" ] && {
    echo "hello" ;
    echo "world" ;
} || { 
    echo "bye bye" ;
    echo "world" ;
}