What is the best way to write if else condition for 3 Boolean variable-CodePudding

I have 3 boolean variables a,b and c. what's the best way to write the if else condition(or some better way) in bash to cover all combinations (refer pic).

for example: a=y,b=y and c=y then echo foo

I can write multiple elseif conditions but is there any alternate way?

CodePudding user response：

Not really sure of what you're expecting precisely, but if you need to check every possible combination, and your variables can only have two values: y or n, then you can use a case statement:

case "$a$b$c" in
    yyy) echo bar ;;
    yyn) echo foo ;;
    yny) echo foo ;;
    ynn) echo foo ;;
    nyy) echo bar ;;
    nyn) echo foo ;;
    nny) echo foo ;;
    nnn) echo foo ;;
    *) echo error; exit 1 ;;
esac

CodePudding user response：

I would do it with an associative array:

declare -A arr=(
   [yyy]=foo
   [ynn]=bar
   [yyn]=bar
   [nyn]=bar
   [nyy]=foo
   [nny]=bar
)

echo ${arr["$a$b$c"]}

CodePudding user response：

You will normally encounter 8 cases but if those 6 are all you face, then you can try something like

if [[ $b && $c]];
then
  echo foo;
else
  echo bar;
fi

This will work because regardless of what a holds, the result foo is y only if b and c are y (True). The rest are just boo. If you want more accurate boolean expression you can try using "k-maps".

CodePudding user response：

case $a/$b/$c in
    [ny]/y/y)       echo foo ;;
    [ny]/[ny]/[ny]) echo bar ;;
    *)              echo error; exit 1 ;;
esac

By adding a separator string (the / in $a/$b/$c), invalid input such as a=yyy b= c= will be rejected as an error.