Arrays provide a method of grouping a set of variables. Unlike in many other programming languages, in bash, an array is not a collection of similar elements. If you want to detect an array with empty elements, like arr= ("" "") as empty, same as arr= () You can paste all the elements together and check if the result is zero-length. And it's short and elegant! This might be little tricky. IsDeclared_Tricky baz: 0 Bash If File Exists. ... or the incorrect answer could be downvoted by the more discerning among us, since @prosseek is not addressing the problem. Method 3. Did I make a mistake in being too honest in the PhD interview? -z "${var+}" to check if the variable is defined/set (even if it's empty). In Europe, can I refuse to use Gsuite / Office365 at work? I want to check if the length of a bash array is equal to a bash variable (int) or not. This only works for named variables (including $_), not certain special variables ($!, $@, $#, $$, $*, $?, $-, $0, $1, $2, ..., and any I may have forgotten). @HelloGoodbye The positional parameters can be set with, uh. Now, to check if a variable is not empty (which means it must be defined), you could use test -n "$var". You fixed just the ones that are actual coding errors (instances of unwanted indirection when working with variables). That is to say, if var='', then the above solution will output "var is blank". A simple one-liner to set default MY_VAR if it's not set, otherwise optionally you can display the message: To clearly answer OP's question of how to determine whether a variable is set, @Lionel's answer is correct: This question already has a lot of answers, but none of them offered bona fide boolean expressions to clearly differentiate between variables values. Also, using the name of the variable without the $ prefix also works: @joehanna Thanks for catching that missing, The first test is backward; I think you want, The second part of the answer (counting parameters) is a useful workaround for the first part of the answer not working when, I'm baffled that none of the other answers mention the simple and elegant. Bash Until Loop Bash Until Loop is a loop statement used to execute a block of statements repeatedly based on the boolean result of an expression. In this case, doing so adds even more (hidden) crudeness: Because I first had bugs in this implementation (inspired by the answers of Jens and Lionel), I came up with a different solution: I find it to be more straight-forward, more bashy and easier to understand/remember. How far would we have to travel to make all of our familiar constellations unrecognisable? Thanks for contributing an answer to Stack Overflow! Bash does not segregate variables by “type”, variables are treated as integer or string depending on the context. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. x That does the same thing in either of ksh93 and bash.It looks like possibly all variables are arrays in those shells, or at least any regular variable which has not been assigned special attributes, but I didn't check much of that.. As of bash 4.2, you can just use a negative index ${myarray[-1]} to get the last element. Accessing array elements in bash The first element of an array starts at index 0 and so to access the nth element of array you use the n -1 index. Join Stack Overflow to learn, share knowledge, and build your career. This is often wrong because it doesn't distinguish between a variable that is unset and a variable that is set to the empty string. The operator -n returns true if the operand is a non-empty string. 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Dedicate this answer 's not foolproof table it is assigned, otherwise it the.