bash shell script case statement for two variables

Question

I want to create a case statement including two expressions, my imagination is to look like this :

a=true
b=false 

case [ "$a" || "$b"]  in  #<-- how can I do this with a case statement ?

true)echo "a & b are true" ;;
false)echo "a or b are not true" ;;

esac

Is it possible to do it with case instead of if ?

Thanks

A case statement doesn't "include" variables, see help case. It is case word in ..., which means you could write case "foo" in "foo") echo "foo found" ;; esac. — Micha Wiedenmann
– Micha Wiedenmann, Commented Sep 1, 2016 at 7:09
ok , I mean expressions - the syntaxis is case statement in , is there a way to use two expressions in one case statement ? Example : 'case expression1 & expression2 in' or 'case expression1 or expression2 in' ? — zlobul
– zlobul, Commented Sep 1, 2016 at 7:15
This might help tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_03.html — Inian
– Inian, Commented Sep 1, 2016 at 7:15
In case WORD in , WORD must be a character string. Therefore the problem is how to turn a logical operation result into a string. As I said, the bash arithmetic $((···)) returns a string, unlike [···] and [[···]] do, but their logical outcomes can be checked using $?. — Jdamian
– Jdamian, Commented Sep 1, 2016 at 8:13
Store the result of a $a or $b in a variable and then use a case statement on that variable. — xxfelixxx
– xxfelixxx, Commented Sep 1, 2016 at 8:21

James Brown · Accepted Answer · 2016-09-01 08:57:36Z

4

This is an example but it's about strings, not real logical expressions:

$ cat > foo.sh
a=true
b=false
case $a$b in        # "catenate" a and b, two strings
    *false*)        # if there is substring false (ie. truefalse, falsetrue or falsefalse) in there
        echo false  # it's false
        ;;
    *)
        echo true   # otherwise it must be true
        ;;
esac

$ bash foo.sh
false

edited Sep 1, 2016 at 8:57

answered Sep 1, 2016 at 8:48

James Brown

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Comments

chepner · Accepted Answer · 2016-09-01 11:36:22Z

2

bash doesn't have Boolean constants; true and false are just strings, with no direct way to treat them as Boolean values. If you use the standard encoding of 0 and 1 as Boolean values, you can use $((...)):

a=1  # true
b=0  # false
case $(( a && b )) in
  1) echo 'a && b == true' ;;
  0) echo 'a && b == false' ;;
esac

answered Sep 1, 2016 at 11:36

chepner

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