Hi,

I trying to test two condition together (AND) under bash but it’s not working…

The goal is ti have True when two variables are either not set or empty (empty string)

I’ve tried

if [[ -n VARIABLE1 && -n VARIABLE2 ]]; then
    echo "OK"
fi

Here I get the “OK” no matter what .

Thanks.

  • Dion Starfire@sh.itjust.works
    1·
    6 hours ago

    You’re probably wanting [ -z "${VAR1}" -a -z "${VAR2}" ]. Note in bash that there are minor differences in how [ ] and [[ ]] tests are handled. You can pull up a handy cheat sheet of the operands on most distros by running man test, though you’ll need to read through the CONDITIONAL EXPRESSIONS section of man bash if you want to see the minor differences of the single vs double square bracket commands (mostly whether locale applies to string order, as well as whether operands are evaluated in numeric comparisons).

  • Rick_C137@programming.devOP
    3·
    1 day ago

    Thank you all for yours input

    What finally did work

    if [[ -z VARIABLE1 && -z VARIABLE2 ]]; then
    echo "OK"
fi

    If only Linux was using Python syntax that would be so much more intuitive…

    • Farnsworth@lemmy.world
      2·
      6 hours ago

      Never use a && b || c. It is not the same as if a; then b; else c; fi: when a succeeds but b fails, it will run both b and c.

      I would not bother with [ unless you absolutely need compatibility with non-bash shells.

    • suff@piefed.socialEnglish
      13·
      2 days ago

      Explanation

      [ is an alias for the program test, so you can call man test for more info.
      && is bash syntax for conjunction. In A && B, B will only be called if A returned a exit code >0 (error). You can call man bash for more info.
      || is bash syntax for disjunction. In A || B, B will only be called if A returned exit code =0 (success). true and false are programs that just return exit codes 0 respectively 1.

    • Farnsworth@lemmy.world
      1·
      6 hours ago

      in [[, empty strings are falsy, so this also works:

      [[ ! $VARIABLE1 && ! $VARIABLE2 ]] && echo "OK"
  • kittenroar@beehaw.orgEnglish
    3·
    2 days ago

    You need to reference the value of the variable, ie:

    if [[ -n "$VARIABLE1" && -n "$VARIABLE2" ]]; then
    echo "OK"
fi
      • kittenroar@beehaw.orgEnglish
        2·
        18 hours ago

        Then it is working. That is what that code was checking for.

        Specifically, -n checks if the variable exists and also does not have a null value.

        If you want to reverse it, ie, check that those conditions are not true, put an exclamation mark in front of the whole thing.

  • thingsiplay@beehaw.org
    2·
    2 days ago

    Try this:

    #!/usr/bin/env bash

a=""
if [[ -z "${a}" && -z "${b}" ]]; then
    echo "OK"
else
    echo "Not OK"
fi

a="OK"
if [[ -n "${a}" && -z "${b}" ]]; then
    echo "More ${a}"
else
    echo "More Unokay"
fi