Bash boolean expression and its value assignment

Question

Is there a way to to evaluate a boolean expression and assign its value to a variable?

In most of the scripting languages there is way to evaluates e.g

//PHS $found= $count > 0 ;  //evaluates to a boolean values 

I want similar way to evaluate in bash:

BOOL=[ "$PROCEED" -ne  "y" ] ;  

This is not working and tried other way but could not get a boolean value. IS there a way to do this WITHOUT using IF ?

Answer 1

You could do:

[ "$PROCEED" = "y" ] ; BOOL=$? 

If you're working with set -e, you can use instead:

[ "$PROCEED" = "y" ] && BOOL=0 || BOOL=1 

_{BOOL set to zero when there is a match, to act like typical Unix return codes. Looks a bit weird.}

This will not throw errors, and you're sure $BOOL will be either 0 or 1 afterwards, whatever it contained before.

Answer 2

I would suggest:

[ "$PROCEED" = "y" ] || BOOL=1 

This has the advantage over checking $? that it works even when set -e is on. (See writing robust shell scripts.)