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  • It seems as if the -n test is not needed. If the variable contains no value, it will not be equal to the string null (if that is supposed to be a string at all, sometimes people seems to thing it's a special value that denotes "no value"). Commented Dec 10, 2018 at 18:10
  • @Kusalananda Yeah, I just wrote this for the benefit of the understanding and syntax of the OP, besides being short in time. I also noticed the first condition is redundant. As for the actual string "null", some utilities indeed return "null" as a full string, in specific situations when they have nothing else to return or have not met a condition...jq is one of them, for instance, and in the past I found more doing that. Commented Dec 10, 2018 at 18:46
  • @Kusalananda taken from a script of mine here using jq too: if [ x"$S" == x"null" ] # end of array Commented Dec 10, 2018 at 18:50
  • @Tomaz is incorrect (though I could not find the referenced post). [ is not bash syntax and you cannot use && inside since [ is a command. bash syntax ([[) does support using && and || inside its test operators. Regardless, testing -n has no effect in this particular case Commented Jan 16, 2020 at 20:56